Cycling,

I think what you are looking for is VLOOKUP()

Sample:
=VLOOKUP(code_from_master,array_codeandquant_supplier,2,false)

I would recommend you just lock the array_codeandquant_supplier to the other workbook, then you should be able to select the first code_from_master cell for the formula and drag the formula down to autofill the values.

HTH,

RC