Remove Collapse/expand icons from the tray for all user except administrato

Hi,

My requirement is to remove the expand/collapse icons from the overview page for all the user but administrator can have those available.

I have set the show tray property to NO , this has made the complete tray invisible for all including the administartor as well.

I want the only icons to be inviisble and not for administrator.

Please provide your valuable inputs.

Thanks

Pooja