If cell is empty and macro is pressed display error message.

Hi I've got the macro code here and I can't figure out how to do that, if the macro is pressed and cell D2 and cell A12 is empty there will be error message like "please fill in the invoice" and if those cells are filled in the macro will run.
Please can you help me.

I'm new here but i think you might want to go read the forum rules located @

http://www.excelforum.com/forum-rule...rum-rules.html

I believe the people who will be able to help you will want the file and or code your are using that gives you that error.