Quick and dirty method.

I added the keyfield to the subforms (hidden). Then on the After_Update field on the Master form, I have the following code (snip)

strNewKey = fldKey (form Master Form)
Hardware!fldKey = strNewKey
Positions!fldKey = strNewKey

I have two subforms, 1 called Hardware and the other called Positions. May not be elegant, but it works!

The reason, that I have found, that it is not working, is that there is no record to link to for the subforms. And yes, to the best of my knowledge, I have all the relationships set correctly along with all the linking.