Taking a parameter from recordsource of form to open a new form in ms access vba.

[HiGu]

I have a procedure that opens a form based on a particular "A_ID".This A_ID is present in the recordsource of a subform but it's not displayed on the same.How do I refer to this A_ID so as to open the form?
As of now A_ID used to come from a combobox which had A_ID in its select query.

forms![frmMain]![cboID]

Now, I do not know how do I take A_ID from the subform as it is not displayed in any of the controls.

[NeoPa]

See if the fields are available (The RecordSource of a bound form has fields). If not, then you may need to include a hidden control bound to that field for this purpose.