Hide a panel on an modalPop up.

Dear all,
I'm calling the show method of an modalPopup extender, but just before that I hide an panel on the  modalPopUp (panel) that the extender will show. Now that's theory becaus it doesn't hide that panel.
To hide the panel I use:

panelToHide.style.display = 'none';Maybe it is not possible to do that ?



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