Hi, kbschmidt77!
Perhaps you'd want to read the three green sticky posts at this forums main page so as to know the guidelines that will lead to know how this community operates (introducing yourself, posting files, netiquette rules, and so on).
And about your question:
If you don't get involved with WeekNum values in individual cells and if they're only part of your formulas and calculations, I'd strongly suggest to try this:
=(B2-A2)/7
Rounding up or down with ROUND, ROUNDUP or ROUNDDOWN functions if needed integer values and wants to round symmetrically, to next integer or truncate, respectively. They're all available since 2003 version at least.
Regards!