The problem with your syntax is that datediff requires 3 parameters:
The format of difference, and the two dates
such as DateDiff("d", Rs("b"), Rs("c"))
check this out, it should give you the answer you need:
http://www.w3schools.com/vbscript/func_datediff.asp
And remember - Google is your friend:
http://www.google.com.au/search?hl=e...datediff&meta=
Try it some time.
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