Hi Mohammed,

If you haven't done this, try this..

Not sure what is the value of "thisform.text3.value"
>thisform.text1.value-thisform.text2.value=thisform.text3.value
>thisform.text4.value-thisform.text5.value=thisform.text6.value
>at thisform.text7.value=(thisform.text3.value+thisform.text6.value)*($11.90)

Below is a sample of Subtracting Time from two text boxes...get the spent time & multiply with a pre-defined rate...

STORE TTOC(CTOT(thisform.text2.value)-CTOT(thisform.text1.value)+{^2000/01/01:},2) TO tTime_spent 
Thisform.txtTime_spent.Value = SUBSTR(tTime_spent,1,5)

STORE SUBSTR(Thisform.txtTime_spent.Value,1,2) TO thour
STORE SUBSTR(Thisform.txtTime_spent.Value,4,2) TO tMinute
nTime= tHour+"."+tMinute
ybill_charge = Val(nTime) * yEmp_rate