Link Child Fields / Link Master Fields Autofill

I have a form for adding and deleting records from a table. It also contains
a subform which displays the records from that table. I want to give the user
the ability to select a specific group of records to be displayed on the
subform. On the Update property of a control I am using to filter, in code I
re-set the subforms recordsource, however, the Link Child Fields & Link
Master Fields keeps defaulting to the Table's Keys every time I do this. I
have deleted these values, but they keep appearing. The subform won't display
the correct records while these values are filled in.