God damn i just thought to...... lets so complecated :-d .
So Lets say three plates :
Left : Have to be active
middle : Have to be deactive
right : Have to be active
So i make a counter now with value 2 :
Left gets active: counter -1
Left gets deactive : counter +1
middle = nothing happen
right gets active: counter -1
right gets deactive: counter +1
And sorry Drakkan i dont know why i dont understand that from the beginning O_O.