Removing duplicate records

hi, how do I delete duplicate invoice rows in excel?

like say if the rows below are like this

Invoice no.

Value

Inv date

459216

$500,169

21/02/2009

459216

$500,169

I want the entire second row to be automatically deleted even though it doesn't have the invoice date in it. But I want excel to pick up that they are duplicates by looking at the invoice numbers and keeping the first entry only! Is that possible? thanks

Taz