Delete rows beginning with !, Add new first row.

Hello,

I am trying to make a complex spreadsheet that will import .s2p files (just text files with a different extension) containing some data, each to a different sheet, delete the beginning comment rows, add a row that has headings describing the data.

All of that for the raw data files (between 1 and ~30 files), a reference file, and an ideal file. I then want to so math on each of the data files with the reference file. After all that I need to do math on the new data with regards to the ideal file and make plots.

I have gotten as far as importing the -space- delimited .s2p files by copying and editing code I've found on the internet. I need help deleting the comment rows (all the first rows that begin with ! can be anywhere from 0 to 12 from what I've seen, and possibly more, as there is no practical limit) and adding a row with headings (instead of leaving a row and overwriting the cells, causing a text box that warns that there is already data here).

Any other suggestions about how I butchered the code together and/or any improvements I could make is also welcome.

Sub import_multiple_s2p()
    Dim xFilesToOpen As Variant
    Dim I As Integer
    Dim xWb As Workbook
    Dim xTempWb As Workbook
    Dim xDelimiter As String
    Dim xScreen As Boolean
    xScreen = Application.ScreenUpdating
    Application.ScreenUpdating = False
    xDelimiter = "|"
    xFilesToOpen = Application.GetOpenFilename("Text Files (*.s2p), *.s2p", , "Import *.s2p files", , True)
    If TypeName(xFilesToOpen) = "Boolean" Then
        MsgBox "No files were selected", , "Import *.s2p files"
        GoTo ExitHandler
    End If
    I = 1
    Set xTempWb = Workbooks.Open(xFilesToOpen(I))
    xTempWb.Sheets(1).Copy
    Set xWb = Application.ActiveWorkbook
    xTempWb.Close False
    xWb.Worksheets(I).Columns("A:A").TextToColumns _
      Destination:=Range("A1"), DataType:=xlDelimited, _
      TextQualifier:=xlDoubleQuote, _
      ConsecutiveDelimiter:=True, _
      Tab:=False, Semicolon:=False, _
      Comma:=False, Space:=True, _
      Other:=True, OtherChar:="|"
      'Rows("1:6").Delete
      

    Do Until ActiveCell.Value = "#"
        Selection.EntireRow.Delete
    Loop
      
      Cells(1, 1).Value = "MHZ"
      Cells(1, 2).Value = "S11 MAGNITUDE"
      Cells(1, 3).Value = "S11 PHASE"
      Cells(1, 4).Value = "S21 MAGNITUDE"
      Cells(1, 5).Value = "S21 PHASE"
      Cells(1, 6).Value = "S12 MAGNITUDE"
      Cells(1, 7).Value = "S21 PHASE"
      Cells(1, 8).Value = "S22 MAGNITUDE"
      Cells(1, 9).Value = "S22 PHASE"
      Range("A2", Range("A2").End(xlDown)).NumberFormat = "0000"
      Range("B2", Range("B2").End(xlDown)).NumberFormat = "00.000000"
      Range("D2", Range("D2").End(xlDown)).NumberFormat = "00.000000"
      Range("F2", Range("F2").End(xlDown)).NumberFormat = "00.000000"
      Range("H2", Range("H2").End(xlDown)).NumberFormat = "00.000000"
      Range("C2", Range("C2").End(xlDown)).NumberFormat = "000.0000"
      Range("E2", Range("E2").End(xlDown)).NumberFormat = "000.0000"
      Range("G2", Range("G2").End(xlDown)).NumberFormat = "000.0000"
      Range("I2", Range("I2").End(xlDown)).NumberFormat = "000.0000"
    Do While I < UBound(xFilesToOpen)
        I = I + 1
        Set xTempWb = Workbooks.Open(xFilesToOpen(I))
        With xWb
            xTempWb.Sheets(1).Move after:=.Sheets(.Sheets.Count)
            .Worksheets(I).Columns("A:A").TextToColumns _
              Destination:=Range("A1"), DataType:=xlDelimited, _
              TextQualifier:=xlDoubleQuote, _
              ConsecutiveDelimiter:=True, _
              Tab:=False, Semicolon:=False, _
              Comma:=False, Space:=True, _
              Other:=True, OtherChar:=xDelimiter
              'Rows("1:6").Delete
              
                  Do Until ActiveCell.Value = "#"
        Selection.EntireRow.Delete
    Loop
              
              Cells(1, 1).Value = "MHZ"
              Cells(1, 2).Value = "S11 MAGNITUDE"
              Cells(1, 3).Value = "S11 PHASE"
              Cells(1, 4).Value = "S21 MAGNITUDE"
              Cells(1, 5).Value = "S21 PHASE"
              Cells(1, 6).Value = "S12 MAGNITUDE"
              Cells(1, 7).Value = "S21 PHASE"
              Cells(1, 8).Value = "S22 MAGNITUDE"
              Cells(1, 9).Value = "S22 PHASE"
              Range("A2", Range("A2").End(xlDown)).NumberFormat = "0000"
              Range("B2", Range("B2").End(xlDown)).NumberFormat = "00.000000"
              Range("D2", Range("D2").End(xlDown)).NumberFormat = "00.000000"
              Range("F2", Range("F2").End(xlDown)).NumberFormat = "00.000000"
              Range("H2", Range("H2").End(xlDown)).NumberFormat = "00.000000"
              Range("C2", Range("C2").End(xlDown)).NumberFormat = "000.0000"
              Range("E2", Range("E2").End(xlDown)).NumberFormat = "000.0000"
              Range("G2", Range("G2").End(xlDown)).NumberFormat = "000.0000"
              Range("I2", Range("I2").End(xlDown)).NumberFormat = "000.0000"
              
        End With
    Loop
ExitHandler:
    Application.ScreenUpdating = xScreen
    Set xWb = Nothing
    Set xTempWb = Nothing
    Exit Sub    
End Sub

Here is an example of how an .s2p file looks, the formatting is the same (with the first column denoting the frequency, then 8 columns of data following), but the data can go on indefinitely, and there can be any number of comments at the top. It is just a text file with .s2p as the extenstion.

! 1601_04CEQ_ideal.s2p
! NWS
! 8/26/2019 10:34:24 AM
!
# MHZ S DB R 50
0001000	-11.9869613412018	-6.86095044985507	-11.7757294738579	6.65055268129362			-11.7740869872519	6.50071717047084	-11.9889017811843	-6.90445839318914
0002000	-12.1478395142215	-13.5274223754705	-11.3186368807837	12.1377401054047			-11.3204783726508	12.0457324587022	-12.1495222137791	-13.5759406320280
0003000	-12.3978824218565	-19.9476008912170	-10.7063665310503	16.0365072541540			-10.7055937189204	15.9582753458519	-12.3999585947958	-19.9731161429106
0004000	-12.7254200085112	-25.9770379884654	-10.0569823914036	18.4146148956388			-10.0564514996434	18.3522829857238	-12.7304459315608	-25.9881061936197
0005000	-13.1135576381519	-31.5660628010709	-9.44296340650123	19.5969323463763			-9.44456726844048	19.5519274225073	-13.1180376783935	-31.5947075126734
0006000	-13.5428402263997	-36.7084752745453	-8.90080337061143	19.9502176779632			-8.90126539088865	19.9144986536716	-13.5481450222241	-36.7109975753455
0007000	-14.0009541850627	-41.3693620446857	-8.43551337766472	19.7651437439195			-8.43570593726523	19.7237798351639	-14.0103425884525	-41.3803125119039
0008000	-14.4778426300636	-45.6147278734629	-8.04220978605024	19.2365679833136			-8.04401784682552	19.2011620254331	-14.4887164021327	-45.6218021195332
0009000	-14.9588839942019	-49.4711332825090	-7.71440830089274	18.5194497656443			-7.71607488738760	18.4953692685205	-14.9698456622246	-49.4775408650545
0010000	-15.4397356430685	-52.9522831451455	-7.44006413051596	17.7120443380617			-7.44307423186925	17.6918726983683	-15.4585915952417	-52.9675286257783
0011000	-15.9144772054603	-56.1485861040163	-7.20981625896134	16.8598850762220			-7.21322789456511	16.8407554903229	-15.9353774668016	-56.1609410002211
0012000	-16.3835472409347	-59.0445340846255	-7.01902795986857	16.0182436065222			-7.01889838502051	15.9957313287276	-16.4101992153088	-59.0523068713830
0013000	-16.8348219910265	-61.6887175597529	-6.85585248070910	15.1925205249856			-6.85666703712444	15.1811648706871	-16.8657112044794	-61.6931161079084
0014000	-17.2786322093448	-64.1344229841705	-6.71649251256513	14.3896754121143			-6.71893399052141	14.3834008488113	-17.3154478655748	-64.1491089056643

p.s. I assume it would be better to break up any further questions into new posts as opposed to adding to this one, please confirm.

Posted question to MrExcel as well.