Referring to a Control on a PARENT form

That's exactly how you refer to it:

Me.Parent.CostPrice

Except you don't do it from the ControlSource - you do it using the Subform's Current event:

Private Sub Form_Current()
  Me.CostPrice = Me.Parent.CostPrice
End Sub

Thank,

I am not quite there yet.
See attached.
I did what I thought you suggested but the form (frmPriceFind) crashes as you scroll through the records.
DerekImport.zip

You've bound the "CostPrice" textbox to a field named "CostPrice", and that field is not in the Recordsource of your subform. You'll have to bind that control to a Field that is present in the Recordsource of your subform.

BTW: I'm referring to the CostPrice textbox on the SUBFORM. In other words, you've bound the CostPrice textboxe on the SUBFORM to a field named "CostPrice", and that field is not present in the Recordsource of the Subform.

Thanks again LSM,

I am approaching the limits of my knowledge here.

Perhaps , if I forget the approach I have explained and merely tell you my objective.

I want to put a (readonly)field on the sub form that is equal to ;

CostPrice on Parent Form * Markup% on Subform.

What is the best way to achieve this?

Thanks LSM,

That was a superb answer.

Your patience and descriptive powers are much appreciated.