Sir
how can I build total amount in subform -form-
for example
table contais quantity and price for each product
and I want to calculate the total amount must be paid
what I do ?
Total = quantity * price for each product
and how can I write this in unbound box in form

Create a footer for the subform in that footer put an unbound control with the Controlsource of:

=Sum(Quantity*price)