Different target Control id for one modal popup extender

Hi All,
 
I have one Link Button lnkBtn, One Modal PopUp Extender and 3 differnt panel with some controls.
On some criteria I want to show different Panel as a modal popup window on click of Link Button.
 
All panel overwrite when i clicked on link button because target conrol id is same and i am changing the popup control id every time on the basisi of my crieteria.
 
Can anyone tell me how can i achive this?
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