advanced excel ms training - Vlookup refering to another spreadsheet within another workbook

I have cells refering to another spreadsheet within another workbook. This other workbook is changed on a weekly basis and therefor this workbook's name changes eg. Last week the workbook was called "20070928 6Week Programme" and this week a new workbook is created with the name "20071005 6Week Programme"

My original spreadsheet looks up the cell values in the other workbook which changes week on week.

Is there a way were I can have a cell with the reference name to which the look up can refer without me having to change the name of the lookup reference in each cell? The idea is just to change this one reference cell and then have all other cells change automatically?