I've created several workbooks that hold code to manipulate data in other workbooks. We usually open the spreadsheet with the code then open the workbook with the data. Sometimes it involves a 3rd workbook used as a template.
A few computers at the office are running Excel 2013 and these macros will not run on them. Excel 2013 doesn't seem to know that there is more than one workbook open since they appear in their own windows. The macro makes pretty straight forward commands as to which workbooks it wants to work with (Workbooks(1).Activate, Workbooks(2).Sheet(1).Range("A1").Select.....etc). But I get error after error. I create these "utilities" (as I like to call them) on a computer with Excel 2010 and everything works just fine. Some of these utilities even run on machines running Excel 2003 without a problem. Unfortunately I can't get on one of these machines using 2013 to do any debugging. I typically get to see the error, take a quick look at the command that caused the problem and then try to research it. One of the resent errors was a straight forward unhide a column command but the column was already unhidden so it crashed. Excel 2010 just ignores the command since it's already unhidden.

Any advice or help to point me in the direction as to what I'm doing wrong would be appreciated.

Thanks