Changing LOOKUP table prices changes previous sales too!

The formula would like this:

=Vlookup(A1,Price_Array, 2, False)

where: A1= lookup_date {change accordingly}

Price_Array = Array of Dates and Prices {I would define a named range}

2 = col_index, {In this case, values are the 2nd column}

False = {Dates and prices do not have to be in order}

Please see attached. If the cost of Cats goes up to $2.00(and in this economic climate that's a real possibility)I change B2 in ProductLookup to reflect that for future sales. However that will chance my cost for the Cat I sold on 6/12/12.

My sense of it that identifying the change by date will cause a new row to be created.

Maybe it would be simpler to us PASTE/SPECIAL/VALUES occasionally.

Thank you ever so much for this help.

Cane