>Hi,
> when i try this
>>>nTimeInHours = (DATETIME()-tStartTime)/3600
>the error message : Operator/Operand type mismatch
>

Then you didn't set tStartTime to a DATETIME() or smething equivalent. The following code works:

tMyStartTime = DATETIME() &&store the DATETIME() result
? TYPE('tMyStartTime')  && should be T - a time variable
tEndTime = tMyStartTime + 100000  && equivalent to waiting 100,000 seconds
? TYPE('tEndTime')  && also T - another time variable
nResultInSecs = tEndTime - tMyStartTime  && I'll bet it's 100,000!
? TYPE('nResultInSecs')  && it's an N - numeric
? nResultInSecs/3600  && should be 27.7778