[AccessD] create cascade combobox

Hello Group, 

i downloaded the create cascade combobox from Candace trip's database. I can't figure out how to store the data from the cascade selection into a headtable.

I have a headtable in which some records are from lookup table (sub).
I use the subtable to create the cascade comboboxes.
How can i store the data in the headtable?

Thanks

Pedro Janssen