Validation for A1 should be:
=AND(ISBLANK(B1),ISBLANK(C1))
Validation for B1 should be:
=AND(ISBLANK(A1),ISBLANK(C1))
Validation for C1 should be:
=AND(ISBLANK(A1),ISBLANK(C1))
Make sure that Ignore Blank is NOT checked.
I will attach a sample copy for you.
+-------------------------------------------------------------------+
|Filename: validation.zip |
|Download:
http://www.excelforum.com/attachment.php?postid=5180 |
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