hi thanks for your help but i don't really understand the second part of your answer.
=[YourSubformContainerControl]![Form]![YourTextBoxName]
what is the subform container control? and do i type in the forms name in the [form] part??
YourSubformContainerControl is the control on the main form that houses the subform. It can be named the same as the subform, but frequenty isn't, so you need to use the container name, instead of the subform name.
Second the word .Form. stays as is. It tells Access that you want to use a property or method on the subform as opposed to the control housing the subform.