I want to program (macro or VB script - I'm not sure which) whenever I open a specific workbook file. I am very experienced in most functions of excel but have never "programmed" in it (i.e., macros or VB script - which do I use). I need some initial guidance to get me started in how to program the following task..

DESCRIPTION OF TASK TO ACCOMPLISH: I want the workbook file to be usable only during a certian trial period. So, when that workbook is opened I want the program to check if the current date is less than the expiration date (stored in a hidden cell) and greater than the most recent used date/time (stored in another hidden cell that is updated by the program each time the file is opened)

Thanks in Advance
Warren