Not completly sure what your asking sorry, though if your wanting to be informed when you click an already selected unit a second time (say a unit in a group of already selected units, or even being informed when clicking the only unit you have selected a second time you can use a unit cllicked triger. To enable clicking events for a given unit go to "Data Editor"->Units and for a given unit disable its 'Unit - Flags'->'Cannot Be Clicked' flag.
Alternatly if you ONLY want the events to fire when you click on a unit that is already selected (rather than whenever clicking a unit selected or otherwise), you can disable this flag (allowing clicking events) in the triger editor on units when you select them, and enable (preventing clicking events) on units when you de select them, therefore only getting informed of clicks on already selected units.
@zpnx: Go
Not completly sure what your asking sorry, though if your wanting to be informed when you click an already selected unit a second time (say a unit in a group of already selected units, or even being informed when clicking the only unit you have selected a second time you can use a unit cllicked triger. To enable clicking events for a given unit go to "Data Editor"->Units and for a given unit disable its 'Unit - Flags'->'Cannot Be Clicked' flag.
Alternatly if you ONLY want the events to fire when you click on a unit that is already selected (rather than whenever clicking a unit selected or otherwise), you can disable this flag (allowing clicking events) in the triger editor on units when you select them, and enable (preventing clicking events) on units when you de select them, therefore only getting informed of clicks on already selected units.