equation in form won't equal

I have a button, that upon pushing is supposed to fill other fields in from
the subform....
1. It worked at one point- and now it won't!
2. is there a better way to do this?

Forms!frm_request!Casefreight =
Forms!frm_request!Frm_Request_Items!sumcasefreight
When I break the code the Casefreight =0 and the sumcasefreight = 42.77.

What is going on?

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