Is your control source a combo box?
You haven't given more details so my personal suggestion is that, if you do
this, then you can based the options on a look up table with two columns.
Column 1: Letters
Column 2: a number to distinguish the ones you need (say 0 or 1).
In the combo box use the table as the source. Make the bound column the
first column and make the second column invisible.
In the after update event:
If [control].Column(1) = 1 then [forms]![main form]![subform].visible = True
You may have to mess around a bit to get it right.

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> I have a control source named" loan type" which is in a form named "frm
> general Infromation subform". If any data in that control source equals
> sd-re, sd-cb, sd-cm, sd-re-sag, sd-cb-sag, or sd-cm-sag then a form would
> show up named "frm call notes document tickler input subform" in a form named
> "document tickler input". Otherwise is would not be visable. How would I
> code that? thanks!!!