You can change either. But you must have the syntax correct.
If you are wanting to change the recordsource for the current form, use:
Me.RecordSource = "NameOfRecordSource"
You cannot use Me.Forms...., because a form does not contain the Forms
collection. You can use that syntax to change the recordsource of a
different form, but you must omit the Me:
Forms.FormName.RecordSource = "NameOfRecordSource"
If you want to change the recordsource of a subform on the current form use:
Me.NameOfSubformcontrol.Form.RecordSource = "NameOfRecordSource"
HTH,
Rob