I'm no expert but I would suggest reinstalling Microsoft VisualBasic
Seeing your version of SolidWorks, this could also be one of the cause:
Thanks for responding back. So if this a cause of microsoft conflict then how do i rectify this?
In your case:
Generally, the SolidWorks installation file includes the all the other installation files, including the one to VisualBasics.
Have you checked if you had the Windows Update KB3072630? I know this one caused some conflicts for a bunch of people, so this could be your cause too.
Has he ever been able to edit the macro? Are you able to edit the macro from another workstation?
If you can edit the macro on another identical workstation then the problem is probably VisualBasics.
If you have a VAR, I suggest contacting them, they will be in the best position to assist you and find out what the problem is.