Changing file names within worksheets

Hello, I am hoping someone may be able to help me.

I am going to go my best to explain what I am looking to do....

my formula is as follows:
=(VLOOKUP(A7,'[Monthly AR Analysis - Feb09.xls]AR - Current'!$A$1:$I$153,8,FALSE))

I will be using this for formula on about 15 different worksheets ... my issue is the file name changes every month and currently I have to go in and do a find and replace, I would like to have one main page where I could change the file name month and it will change all the rest.

ie: Monthly AR Analysis - Feb09.xls next month changes to Monthly AR Analysis - Mar09.xls .... So basically each month I want it to pick up the new file that has been saved with the new name.

So what I would want is to be able to have a cell that I could change the Feb09 to Mar09 and then it would do the same to all the worksheets

Is this possible?

I attempted to use CONCATENATE to change file name and it worked but will not work within the Vlookup....

I would appreicate any advise .... thanks in advance.