Hi ,
A date is basically a number ; to know whether the value in a cell is a number , you can use the =TYPE(...) function , where you need to replace the ... by the cell reference which contains the date you wish to check.
A real date will return 1 , whereas if the date is actually either entered as a text string ( prefixed by a single quote ) or entered in a cell which has been formatted as text , you will get 2.
The DATEVALUE function expects a string parameter ; if you use DATEVALUE with a numeric value , you will get a #VALUE! error.
So , if you are getting a #VALUE! error , it should mean that the concerned date value is a number.
Use DATEVALUE with the date which returns 2 for the TYPE function e.g.
=A1=DATEVALUE(B1)
where A1 contains a valid date , and B1 contains an identical date value which is actually a text string , will return TRUE.
Narayan