Returning values from column A, using searches from Column B

Hi,

Right I have a problem at the moment with a search, below are the worksheets I have

Workbook 1
Col A ............ Col B
1234............... John
2345................Susan
4567................Eric

Workbook 2
Col A..................Col B
<value>..............John
<value>..............John
<value>..............John
<value>..............Susan
<value>..............Susan
<value>..............Eric

I want a formula in Col A in WB2 that checks the name in Col B, using this name to search Col B in WB1 and returning the corresponding value from Col A in WB1. Bit strange I know, however the report that will be in WB2 will be thousands of lines and there will be hundreds of names and ID numbers against them

Thanks

James

Worksheets, sorry.