Try Something like this:
DateTimeVar d1 := {LA966.VEH_USE_BGIN_DT};
DateTimeVar d2 := {LA966.VEH_USE_END_DT};
datediff("d",d1,d2)
-datediff("ww",d1,d2,crSaturday)
-datediff("ww",d1,d2,crSunday) DataDog
'Failure Is Not An Option'