Import multiple text files into different sheets + delimiter

Hey guys, first time posting here, absolutely no experience programming macros, but I did do some vba in high school about 5 years ago, so extremely rusty, let me explain my question.

I have a text file for every month of the year for 4 years and I would like to import them to a single workbook but different sheets. I actually already found a solution to this, a section of code I found (from this forum I think?) I don't remember where I found it, so if the OP of this code could come forward and claim this, much appreciated.

Also, I did hit the sticky but could not find the solution to my first problem, delimiters.
I edited this code so it would ask for the path of the txt files as well as changed it from csv files to txt files.

Sub Example12()
Dim MyPath As String
Dim FilesInPath As String
Dim MyFiles() As String
Dim SourceRcount As Long
Dim Fnum As Long
Dim mybook As Workbook
Dim basebook As Workbook

'Fill in the path\folder where the files are
'on your machine
MyPath = InputBox("Enter", "I Rock")

'Add a slash at the end if the user forget it
If Right(MyPath, 1) <> "\" Then
MyPath = MyPath & "\"
End If

'If there are no Excel files in the folder exit the sub
FilesInPath = Dir(MyPath & "*.txt")
If FilesInPath = "" Then
MsgBox "No files found"
Exit Sub
End If

On Error GoTo CleanUp

Application.ScreenUpdating = False
Set basebook = ThisWorkbook

'Fill the array(myFiles)with the list of Excel files in the folder
Fnum = 0
Do While FilesInPath <> ""
Fnum = Fnum + 1
ReDim Preserve MyFiles(1 To Fnum)
MyFiles(Fnum) = FilesInPath
FilesInPath = Dir()
Loop

'Loop through all files in the array(myFiles)
If Fnum > 0 Then
For Fnum = LBound(MyFiles) To UBound(MyFiles)
Set mybook = Workbooks.Open(MyPath & MyFiles(Fnum))
mybook.Worksheets(1).Copy after:= _
basebook.Sheets(basebook.Sheets.Count)

On Error Resume Next
ActiveSheet.Name = mybook.Name
On Error GoTo 0

' You can use this if you want to copy only the values
' With ActiveSheet.UsedRange
' .Value = .Value
' End With

mybook.Close savechanges:=False
Next Fnum
End If
CleanUp:
Application.ScreenUpdating = True
End Sub

Problem is, the text files have semicolon delimiters and I know that you set delimiter options in the "Workbooks.Open" command but I don't know the syntax.
Also, I need 2 other things, first is a must have, but the second is not needed, it would just be nice.

1) I need to add an extra column to each worksheet that adds certain cells together, eg B2 + C2 + E2, and implement this in the same code as the above.
2) Copy these extra columns from each worksheet into a different workbook, specifying the start and end point for each set of 12 worksheets (Eg 2008 Jan - Dec in the 2008 worksheet, then 2009 Jan - Dec in the 2009 worksheet etc etc)

Thanks a lot!! (Oh does Tapatalk work for this forum by the way?)