Put the following User Defined Function (UDF) in a standard module:
Public Function deflime(J3 As Variant, x As Variant) As Double deflime = 0 result = (J3 + x) / 150 For i = 1 To 9999 deflime = deflime + result If result <= 1 Then Exit Function End If result = x * result / 150 Next i End Function
User Defined Functions (UDFs) are very easy to install and use:
- ALT-F11 brings up the VBE window
- ALT-I ALT-M opens a fresh module
- paste the stuff in and close the VBE window
If you save the workbook, the UDF will be saved with it. If you are using a version of Excel later then 2003, you must save the file as .xlsm rather than .xlsx
To remove the UDF:
- bring up the VBE window as above
- clear the code out
- close the VBE window
To use the UDF from Excel:
=deflime(A1,B1)
To learn more about macros in general, see:
http://www.mvps.org/dmcritchie/excel/getstarted.htm
and
http://msdn.microsoft.com/en-us/library/ee814735(v=office.14).aspx
and for specifics on UDFs, see:
http://www.cpearson.com/excel/WritingFunctionsInVBA.aspx
Macros must be enabled for this to work!
Here is an example: