Linking to Specific Worksheets according to Date

I have a unique situation that I'm hoping I can automate with some help from the experts. I create the billing data for some key accounts and I was asked to build a summary sheet that brought all of them into one place so that the billing department didn't have to open each individual spreadsheet each month to verify their info to mine. What I would like to accomplish is to stay current according to today's date. So if it's March, 10, 2014, I need to update the spreadsheet data according to the February 2014 spreadsheet a Key Account #1. Then in April, I need it to look for the new March 2014 spreadsheet. I'm assuming I can use an =IF(OR(... formula for this, but I'm just not sure how to get the date thing sorted out. As far as naming of the the Key Accounts billing spreadsheets, they go something like 0214 "KeyAcct #1".xlsx. Then the new one will be 0314 "KeyAcct #1".xlsx. Even tho the next months billing file isn't created, the formula should be able to check against the date and know when to look for the new one.

Any great ideas? I'm still tinkering and hope to figure this out, but maybe someone can give a quick answer before I spend hours on this.

Thanks in advance!