a date-time is reuired here - ERROR

[PeriyurParthi]

HI ALL
i have a datetime - typeof parameter named {?Param3}. iam useing this parameter in formula editor as

Select {?Param3}
Case "ID" : totext({EmpMaster.ID })
Case "EmpName" : totext({EmpMaster.empname})
Case "DOB" : totext({EmpMaster.DOB},"dd/MM/yyyy&quot

when i check for errors its giving error as "A DATE TIME IS REQUIRED HERE" in the "ID" field. help and replies will be appreciated

thanks
parthi