Run Macro upon cell changed by formula

Hello, I'm trying to run a macro, using Visual Basic, upon the change of a cell which is based on a formula. I know the worksheet_change function only evaluates manually inputted data values and not data updated by a formula. Any help would be greatly appreciated and thanks in advance.

I added your code to the view code page on the sheet and changed the cell to c3(where the BLP formula is) and have made a macro called "Macro1" and replaced it where you wrote "yourmacroname". Macro 1 simply outputs a msgbox but it does not execute upon the data change in cell c3. I don't know if this is important but cell c3 is a blp function streaming in live RTD data. Am i doing something wrong? I'm quite a noob at Visual basic so any extra detail you could provide would be greatly appreciated. Thanks, Dennis.

Thanks for your sheet. It works well for regular formulas but doesn't seem to work for streaming data that updates itself.

I tried using the Worksheet_Calculate function in place of the worksheet_Change function but am having problems. Where in the code do I place the worksheet_calculate function? I tried to replace the change with calculate. Sorry for being such a noob. I'm using the attached file above. Thanks, Dennis.