Hi Gerard,
This all makes sense to me. I would guess if your mouse cursor is over the form and you press F10, it would probably work. The form with the private session should be and is in charge of the data. You can't just use it willy-nilly outside the form. MyPrg1 works when called inside the form. But the OKL calls it from somewhere else--perhaps.
Rather than messing with DataSessionIDs, just call a method in the form.
Example:
WrapperForF10.PRG
IF TYPE("_SCREEN.ActiveForm")=="O" AND PEMSTATUS(_SCREEN.ActiveForm, "YourMethod", 5)
_SCREEN.ActiveForm.YourMethod()
ENDIF

Now the work is being done in the session.

>Hi,
>
>I have a Private Data session form , with one File in DE (called KMA)
>Also have a simple MyPrg1.prg with two lines:
>Sele KMA
>Brow
>
>I have two buttons, each which call MPPrg in different way
>MyButt1: Do MyPrg1
>MyButt2: On Key Label F10 do MyPrg1
>
>If I click button 1, Mprg1 runs ok
>If I click Button 2,and F10, I get an error saying Alias Kma not found
>
>Now if I change the screen to a Deafult Data session, all is ok !!
>
>Is there some inherent problem using Private datasessions and an On Key Label ??
>
>If so, is there a workaround. In my calling prg, I want to set a few on key label commands so tht they stay in place for the duration of the app.
>
>Any help appreciated.
>regards,
>
>Gerard