First of all, it would be easier to determine the problem if you posted a .cap.
Okay, so I'll try and run through how to make a simple selection and de-selection .cap.
First create sprites sprite1 and sprite2, box dragbox, and mousekeyboard
Next, give dragbox the selection box behavior, and sprite1 and sprite2 the RTS behavior
Thirdly, create the private variable for both sprite1 and sprite2 called selected with the text value "no"
Then add the following to the event sheet:
on left clicked on sprite1 -> sprite1: set 'selected'(the private
variable) to "yes"
on left clicked on sprite2 -> sprite2: set 'selected'(the private
variable) to "yes"
pick all sprite1 in selectionbox | sprite1: set selected to "yes"
(from dragbox behavior) _____ ->
pick all sprite2 in selectionbox | sprite2: set selected to "yes"
(from dragbox behavior)
on right mouse button clicked -> sprite1: set selected to "no"
sprite2: set selected to "no"
on left clicked
Sprite1: Value 'selected' is -> Sprite1: move to mouse (RTS
equal to "yes" behavior)
on left clicked
Sprite2: Value 'selected' is -> Sprite2: move to mouse (RTS
equal to "yes" behavior)
Sorry for the rough formating. Hope it helps.