Datediff query

HelloI have added a calculated field into a dataset which uses this expression:=DateDiff("d",Fields!Date.Value,Now) This works fine if there is a value in fields!date.value. However, if that field is blank, it returns the value 735793.Is there any way I can get the expression above to say 'no date input' if the field is blank and still work as above if a date has been entered?Thanks.