=MIN(IF(Sheet1!A2:A100=A2,Sheet1!B2:B100))

which is an array formula, so commit with Ctrl-Shift-enter not just Enter

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HTH

Bob

"dcr" wrote in message
...
I have inherited a spreadsheet with a formula that does not work. Instead
of
returning the earliest order date it returns the first order date. I
would
like a formula to place in Sheet 2 that would populate the earliest order
date.

Sheet 1

Part Number Order Date
111 9/10/2007
113 1/1/2007
111 1/1/2007
113 2/1/2002

Sheet 2

Part Number Earliest Order Date
111 1/1/2007
113 2/1/2002

Thank you in advance!