Help with an excel formula

Hi All,

I'm trying to make a spreadsheet at work and attached is a basic version of what i'm trying to do. Mainly concentrating on tab "sheet 2" this will be a log sheet for recording invoice numbers paid against agency staff members.
Col A = staff ID number. I have used the data validation tool/ list so we can select any of the staff ID numbers from the first tab "sheet 1"in column A
Col B = Weekending dates (sundays) and as above I have currently created a list you can select from from the first tab using row 2
Col C = this automatically selects the surname to match the staff ID number from tab 1
Col D = we will type in the invoice number
Col E = the date we sent this to accounts payable to process and pay the invoice

Basically what I am trying to do is be able to create a list to log the invoices I approve which containing what the invoice number is, who the payment relates to and what week ending the payment covers.

What I'm stuck with is I need the spreadsheet to some how alert me if I am entering a staff ID number and a W/E date which has already been entered before. As with the attachment rows 7 and 8 on tab 2 both contain staff ID 1 (smith) with 2 invoice numbers containing the same w/e date. Is there some sorta way I can have a spreadsheet that will highlight any rows that have identical data in columns A and B?

Also not as important I was tring to find a way that on tab 1, could the green section automatically update itself with the invoice number using data from tab 2?

Any help will be well appreciated!!

cheers shane

Use Conditional Formatting
Try

=(SUMPRODUCT((A$4:A4=A5)*(B$4:B4=B5))<>0)

and format as required for your highlight

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