Dialog position relative to command link component

[Renju]

Hi,
I am trying to use the below syntax to position my dialog just below my command link. But its not working and moreover, the dialog position is changing whenever I am scrolling the page up or down.

<p:dialog context="'mainForm:commandLinkA','tl','br'" widgetVar="TreeDlg" header="Select " draggable="false">

Any help is appreciated.

Thanks and Regards,
Renju