Lookup & Match - Find WK # of last entry

Hi All,

I have 2 separate worksheets;
Sheet 1 is my table of raw date, with 2 headings (ColA = WK# and ColB = Job#)

Sheet 2, ColA = WK# and ColB = formula in sheet2 B2 to calculate the last WK# from sheet 1 which there is a record of the job number referenced in Sheet2 A2