Problem with trying to run the Merlin program on 2008 Excel

Hello, for my biology class, I'm supposed to be installing the Merlin software into Microsoft Excel as an add-in. I got the Merlin program from my teacher, and it seems to work fine for the rest of my classmates. However when I try to install the add-in into excel, I get the message,"The basic visual add-in cannot be loaded. - Visual basic add-ins do not work in Office for Mac".

How do I get the Merlin software to work on my computer? Is it necessary for me to buy the 2011 version of Microsoft Office in order for this to work?

Other information that might be useful:
I'm using a Mac OS X, Version 10.5.8
My version of Microsoft Excel is 2008, and the merlin software comes in xla format.

Sorry, I'm kind of clueless when it comes to computer related stuff.

Office 2008 does not support VBS, therefore Merlin will not work. You need to upgrade to Office 2011 where VBS and macros are once again supported. Your classmates are probably running the Windows versions of Office where VBS is supported across the versions.