I may have been asking the wrong question, sorry.
I had problems with ServerFilter getting stuck....read about that a bit, so then I abandoned that and tried setting it through code, which worked but briefly showed the old record before it refreshed, which bothered me.
so then I tried an SP (using other examples I found here) and it was nothing but problems, and I can't see putting 57 lines of code in to open to a single record...!!
I found a better way to bind a filtered record source to a form -- SQL string in the OnOpen event for RecordSource using a Global as a parameter...it appears to work well.
Me.RecordSource = "SELECT * " _
& " FROM dbo.tblCustomers" _
& " WHERE (Customer_ID = " & Cust & ")"
-- global 'Cust' having been set from the prior form that opened this form
only thing then is I have to set all the subforms' Child & Master links to nothing, setting them through code instead.
Seems they look to establish the links prior to the OnOpen event, causing a parameter prompt.