Here's my Expression:--It Occurs a problm while checking NULL value comes in the field.
=IIF(IsNumeric(Fields!TechHours.Value.ToString),
IIF(Right(Fields!TechHours.Value,Instr(Fields!TechHours.Value,"."))>0,
Fields!TechHours.Value,
Left(Fields!TechHours.Value,Instr(Fields!TechHours.Value,".")-1)
),
"NU"
)