Using VBA to apply Conditional Formatting based on a calculation to Column

Hi Phil. Thank you for doing this. Works a treat but unfortunately it is not quite what I need. I did not explain clearly - Sorry to have got you to do the work.

These 3 columns are going to be input fields and their values can change. The conditional formatting is to let the user know if the values should be looked at. Hence if on start up col 1 + col 2 = col 3 then the formatting would be blank. If someone enters a value in any of the 3 columns that makes col 1 + col 2 <> Col 3 then the background in col 3 goes red until they correct the values.

What I need is the code to set the conditional formatting on column 3. I believe it is a function called "FormatConditions"

Hope this makes it a bit clearer.

Many thanks again.

Tony