Macro to update data using VLOOKUP Function

Hi guys,

I have a bit of a problem.

I have 2 workbooks, with one workbook being a large data store, and the other workbook a number of sheets that use the VLOOKUP function to pull data out of the data store when certain values are inputted.

I was wondering if there was any way that I could write a Macro to update the fields when the "unique lookup value" is entered.

Or would I still need to have the other workbook open?

If I require the other book open, how would I write a macro so at the push of a button the data store workbook would open up?

Thanks!

Nick