Run export macro on different sized ranges in every worksheet with same starting cells

I have a macro that I run repeatedly in a certain type of spreadsheet that does an export on a selection, pulls up a "Save As" message box and saves as a text file. There are 9 sheets in the workbook that contain the same data analysis for a set of samples, the only difference between them being the number of data (e.g. some may have 1500, 1400, 1600, etc.). I only select three columns of data to export (I6:K????) that contain counts (1,2,3,....), x-coordinates and y-coordinates. The counts column (I) uses a formula that only counts if there is an x-coordinate next to it (Col J).

=IF(ISBLANK(J6),"",ROW(J6)-5)

Generally, what I do to make quick work out of selecting the variable ranges is to select Sheets 03-11 (the first nine sheets) and select K6:I6 (starting w/ K6). Then, on each individual sheet, I do CTRL+SHIFT+DOWN to select all the relevant data (if I started my selection with I6, then it would select all cells that contained formulas which may or may not have x,y-coordinates adjacent to them). Once the data is selected (I6:K????), I run the export macro and save the data as text. I would like a macro that can automate the selection for each Sheet 03-11, excluding Sheets "all", "data" and "summary", and run the export macro, first prompting me for a file location and a file prefix. When the text file is saved, it uses the file prefix and Worksheet name to build the filename, i.e. "path\prefix_wkshtname". I'd greatly appreciate anybody's help on this.

I've attached an example workbook.
Here are the export codes, which were taken from

HTML Code: 

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''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' ExportToTextFile
' This exports a sheet or range to a text file, using a
' user-defined separator character.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Public Sub ExportToTextFile(FName As String, _
    Sep As String, SelectionOnly As Boolean, _
    AppendData As Boolean)

Dim WholeLine As String
Dim FNum As Integer
Dim RowNdx As Long
Dim ColNdx As Integer
Dim StartRow As Long
Dim EndRow As Long
Dim StartCol As Integer
Dim EndCol As Integer
Dim CellValue As String


Application.ScreenUpdating = False
On Error GoTo EndMacro:
FNum = FreeFile

If SelectionOnly = True Then
    With Selection
        StartRow = .Cells(1).Row
        StartCol = .Cells(1).Column
        EndRow = .Cells(.Cells.Count).Row
        EndCol = .Cells(.Cells.Count).Column
    End With
Else
    With ActiveSheet.UsedRange
        StartRow = .Cells(1).Row
        StartCol = .Cells(1).Column
        EndRow = .Cells(.Cells.Count).Row
        EndCol = .Cells(.Cells.Count).Column
    End With
End If

If AppendData = True Then
    Open FName For Append Access Write As #FNum
Else
    Open FName For Output Access Write As #FNum
End If

For RowNdx = StartRow To EndRow
    WholeLine = ""
    For ColNdx = StartCol To EndCol
        If Cells(RowNdx, ColNdx).Value = "" Then
            CellValue = chr(34) & chr(34)
        Else
           CellValue = Cells(RowNdx, ColNdx).Value
        End If
        WholeLine = WholeLine & CellValue & Sep
    Next ColNdx
    WholeLine = Left(WholeLine, Len(WholeLine) - Len(Sep))
    Print #FNum, WholeLine
Next RowNdx

EndMacro:
On Error GoTo 0
Application.ScreenUpdating = True
Close #FNum

End Sub
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' END ExportTextFile
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''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' DoTheExport
' This prompts the user for the FileName and the separtor
' character and then calls the ExportToTextFile procedure.
' http://www.cpearson.com/excel/ImpText.aspx
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Sub DoTheExport()
    Dim Filename As Variant
    Dim Sep As String
    Filename = Application.GetSaveAsFilename(InitialFileName:=vbNullString, FileFilter:="Text Files (*.txt),*.txt")
    If Filename = False Then
        ''''''''''''''''''''''''''
        ' user cancelled, get out
        ''''''''''''''''''''''''''
        Exit Sub
    End If
    Sep = vbTab
    '"vbTab" outputs selection as tab-delimited'
    'to choose separator, use'
    'Sep = Application.InputBox("Enter a separator character.", Type:=2)'
    
    If Sep = vbNullString Then
        ''''''''''''''''''''''''''
        ' user cancelled, get out
        ''''''''''''''''''''''''''
        Exit Sub
    End If
    Debug.Print "FileName: " & Filename, "Separator: " & Sep
    ExportToTextFile FName:=CStr(Filename), Sep:=CStr(Sep), _
       SelectionOnly:=True, AppendData:=False
End Sub
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' END DoTheExport
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