ahhn...sorry forgot to change the column headers in the code.
Nevermind i got it solved:
Here is the code:
Sub LoopThroughSheets()
Dim ws As Worksheet
Dim lRowFound As Long
Dim lColFound As Long
Dim lColFound2 As Long
Dim lngLastRow As Long
'Dim i As Integer
For Each ws In ActiveWorkbook.Worksheets
On Error Resume Next 'Will continue if an error results
ws.Range("A:A").Delete
lRowFound = ws.UsedRange.Find("Header1", LookIn:=xlValues).Row
ws.Rows("1:" & lRowFound - 1).Delete Shift:=xlUp
ws.Range("A:A").Insert
ws.Range("A1") = "ID_Vs"
ws.Range("A:A").NumberFormat = ("General")
lColFound = ws.UsedRange.Find("Header1", LookIn:=xlValues).Column
lColFound2 = ws.UsedRange.Find("Header2", LookIn:=xlValues).Column
'For i = 2 To lColFound
'ws.Cells(2, 1) = ws.Cells(2, lColFound) & ws.Cells(2, lColFound2)
ws.Range("A2").Formula = "=OFFSET(A2,0," & lColFound - 1 & ") & OFFSET(A2,0," & lColFound2 - 1 & ")"
'Next I
ws.Range("A2").Copy
ws.Paste ws.Range("A2:A" & ws.UsedRange.Rows.Count)
Next ws
End Sub