Firstly, if you want to call perl scripts from vb, just use system calls and either use return values or text files as a simple way to pass data back and forth.
It may be worth your time to review Activestate's Guide to Using OLE with Perl. This document gives specifics on how to use Win32 OLE within perl to manipulate Excel, among other things. These techniques might allow you to remove the need for a VB application entirely, depending on the amount of user interaction your program requires.
If it is possible for you to remove Visual Basic from the scene altogether, you can use the advice under How do I convert a VBA macro to Perl? to hack together a script that will help (but not perform a 'total' conversion) convert VB code to perl.