Thanks for your solutionOgilvy! but am not able to make the macro work. And
thanks to all you programmers who has
helpt me with my questions.
(It's not easy to be an Copy and Paste Programmer!)

My problem is that I want to calculate every cell to the right from
"RngMdDp1", based on the value on every cell in "RngMdDp1"That meens
cells(O2:O115). compare to the value in cell (I3)

Example:
The Cell that is used to see witch calculation to use
Cell ("I3") value = 1358

Example of the breaking point I wont in the ("RngMdDp1")
Cell ("O55") value = 1355. Then it uses the first Calculation.
"=(RC[-1]*RC[-2])"
Cell ("O56") value = 1357. Then it uses the first Calculation.
"=(RC[-1]*RC[-2])"
Cell ("O57") value = 1359. Then it uses the second Calculation. "=(RC[-1])"
Cell ("O57") value = 1361. Then it uses the second Calculation. "=(RC[-1])"

I hope that I have explain so you anderstand my problems.
Below is some of the macro I have used. That dont work.
-----------------------------------------------------------------------------------
Sub DrillPipe1()
Dim c as Range
For Each c In Range("RngMdDp1")
If c.Value < Range("I3") Then
c.Offset(0, 1).FormulaR1C1 = _
"=(RC[-1]*RC[-2])"
Else
c.Offset(0, 1).FormulaR1C1 = "=(RC[-1])"
End if
Next c
End Sub
---------------------------------------------------------------------------------
Sub DrillPipe1()
For Each cell_in_loop In Range("RngMdDp1")
If (cell_in_loop.Value Range("I3").Value) Then
cell_in_loop.Offset(0, 1).FormulaR1C1 = _
"=(RC[-1]*RC[-2])"
Else
cell_in_loop.Offset(0, 1).FormulaR1C1 = "=(RC[-1])"

Exit For
End If
Next cell_in_loop

End Sub

Thanks for you'rs time
Aksel