Update Subform field from another Form (1 Viewer)

I have a subform which calls a new Pop-Up form. The user inserts some data into the Pop-Up form, does a calculation and I then want the calculated value to update a field on the Sub-Form.

I have tried this line of VBA (and variations) but it errors saying that the field cannot be found. I must admit, I never quite get this kind of form referencing syntax right without a lot of trial and error. If someone could explain the rationale, that would also be good.

My erroneous code is:

Forms![mainform].[subformname].[Form]!Field.value = PopUpformfield.value

I guess I could do this with an appropriate SQL statement but I was hoping this would be simpler.

Thanks

Here we are:

Notice it should be the name of the control, not the field.

Or using your variation:

Your are indeed a Scholar and a Gentleman. Thank you

You're welcome Ted.

Here's a link for future reference:

http://www.mvps.org/access/forms/frm0031.htm

Marvellous - thanks again.

No problemo!