How to update a Texbox its textvalue

Hi,

I got a form which contains a textbox.

This textbox his source expression is a global variable, namely
gv_TotaalAantalKG.


In the OnAfterGetRecord i place the default value for this variable:
gv_TotaalAantalKG := Rec.AantalKgTotaal;

Now this form also contains a button, wich changes the value of this
gv_TotaalAantalKG on the button press.

<Control1000000038> - OnPush()
gv_TotaalAantalKG := StandaardProductie;

Now the problem is that this new value isnt visible on the form, i only see the old value...

Updating the form doesnt work either

<Control1000000038> - OnPush()
gv_TotaalAantalKG := StandaardProductie;
CurrForm.UPDATECONTROLS;
CurrForm.UPDATE(FALSE);

How can i make the form show the new value on the button press?