Comparing/Matching data across in Excel works

Hello,

I have manually combined 4 separate reports into 1 workbook with 4 worksheets (1 for each report). Each row represents a separate job.

The 1st worksheet is an export from our own Access database, the 3 others come from external reports.

Whilst each report/worksheet contains different sets of data, 1 column in each worksheet contains `CSR' or `Site ID' numbers. These numbers can be used to match the jobs - however a) not every worksheet has every number b) some numbers may appear more than once on the same worksheet (these are essentially returns to the same job).

The 1st worksheet also has a column with OPID numbers (Column A), these are unique numbers that we have paired to a CSR or Site ID number.

I want to compare the numbers in the CSR column of the 1st worksheet (Column B of Sheet 1) with the CSR columns in the other worksheets and where there is a match, copy/add the corresponding OPID number to a blank column in each worksheet.

What would be the best way to do this?