you try this.
suppose you want to enter the correct invoice number in sheet 2
make sheet2 as active sheet
suppose the value of the invoice in all the sheets in G1
then try this macro
KEEP THE MSGBOX SO THAT YOU WILL BE SURE THAT YOU ARE DEALING WITH CORRECT SHEETS.
Dim ws1 As Worksheet, ws2 As Worksheet, r As Range, j As Integer
Set ws2 = ActiveSheet
j = ws2.Index
Set ws1 = Worksheets("sheet" & j - 1)
ws2.Range("G1") = Left(ws1.Range("G1"), 8) & Mid(ws1.Range("G1"), 9, 4) + 1 & Right(ws1.Range("G1"), 4)