How to set RecordSource for sub form

I have inherited an access application front and backend and am converting it to sql server backend.
The code that opens a form is:  [MainSub].SourceObject = "TurtleMain". This form in turn has  several subforms. I have code like this to get records for each of the subforms:

Set rsFeeding = New ADODB.Recordset
With rsFeeding
   Set .ActiveConnection = con
   .Source = "spSubFeeding " & vTurtleID & " "
   .LockType = adLockOptimistic
   .CursorType = adOpenKeyset
   .CursorLocation = adUseClient
   .Open
End With

I want to be able to set the Recordset for the subform, but the code: Set Forms!Main!MainSub.Form!TurtleFeedingSub.Recordset = rsFeeding gives me an error of "object doesn't support this property or method."

What is the correct way to set the Recordset property?