It sounds like you might need two loops here. It depends on how you're getting the list of files to process. Here are two possibilities:
1) If you have the file names in a list:
Code:
For Each file_name As String in file_names
' Process this file.
For i As Integer = 1 To 108
' Do something with line i.
...
Next i
Next file_name
If you use a file method to list the files in a directory, that should work, too.
2) If the user enters a file name in a TextBox and clicks a button, then the button's code can define the variable.
Code:
' Process the file.
For i As Integer = 1 To 108
' Do something with line i.
...
Next i
3) If you want to do something more elaborate such as processing a single line each time the user presses a button, then you might try something like this:
Code:
' Declare LineNumber at the module level outside of any routine.
Private LineNumber As Integer = 0
' Handle the button click.
Private Sub btnProcessLine_Click(...)
' If we don't have a line number, open the next file.
... open a file here ...
' Process line number LineNumber.
...
' Move to the next line.
LineNumber += 1
' If we have processed 108 lines in this file,
' get ready to open the next file.
If (LineNumber > 108) Then LineNumber = 0
End Sub
If you can give us a little more information about how things are controlled, for example how you know which file to open, we might be able to give a bit more help.