In your subform, create a text field (if you have not already done so) to calculate the quantity x unit price. Call this field ExtendedPrice. In the footer of your subform, create a text field and in the control source put =Sum([ExtendedPrice]). Name this field OrderSubtotal. You can choose to leave this field visible set to no.
I am assuming that your sub form is set to datasheet view.
In your main form create another text field and place the following in the control source:
=[SubformName].Form![OrderSubtotal]
Replace "SubformName" with the actual name of your subform.
[This message has been edited by Carol (edited 08-14-2001).]
[This message has been edited by Carol (edited 08-14-2001).]