Thankyou again Richard Buttrey, i love your prompt responses

i don't think i have explained myself good enough, my 1st attachment has no formulas in sheet4 "HIDE" colum D or E
but B2 and C2 would keep a running total from D2 and C2, but everytime any type of formula gets entered into
D2 or C2 the numbers don't add up anymore in B2 and C2, the code in sheet4 "HIDE" stops working.

Private Sub worksheet_Change(ByVal Target As Range)

    If Target.Count = 1 And Not Intersect(Target, Range("D2:E21")) Is Nothing Then
    Application.EnableEvents = False
    Target.Offset(0, -2).Value = Target.Value + Target.Offset(0, -2).Value
    End If
    Application.EnableEvents = True
    
End Sub
Thanks
Keith