The following macro is my crude solution (I sense there may be a much more efficient way to do this) to a need in a multi-line file to insert 99 copies of each line between the existing lines; so a 10 line file becomes a 1000 line file, etc. The macro works on the 1000 line example, but when I tried it on a 20,000 line test file I got an error that the 'clipboard cannot be emptied', debug revealed it was on the line with stars below that the error was occuring. How do I deal with that? Or, alternatively, is there a much better way to achieve the same results?

Thanks in advance,

Rob

Sub Interpolate_NIRS()
numlines = Range("A1").SpecialCells(xlCellTypeLastCell).Row
MsgBox numlines
Application.ScreenUpdating = False
For j = 1 To numlines
ActiveCell.Rows("1:1").EntireRow.Select
Selection.Copy
For k = 1 To 99
ActiveCell.Range("A1:B1").Select
Selection.Copy
ActiveCell.Offset(1, 0).Range("A1").Select
Selection.Insert Shift:=xlDown
**** Next
ActiveCell.Offset(1, 0).Range("A1").Select
Next
Application.ScreenUpdating = True
numlines = Range("A1").SpecialCells(xlCellTypeLastCell).Row
MsgBox numlines
End Sub