If you simply want to identify where duplicates are, then use conditional formatting. Use the following formula for conditional formatting: =COUNTIF($A$1:$C$4,A1)1 The range $A1$1:$C$4 will have to be expanded to include the entire range where duplicate apartment numbers could exist. The cell A1 is the leftmost, topmost cell in this range, and the format can be duplicated to all cells in the range.

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frmsrcurl: http://msgroups.net/microsoft.public...licate-numbers