You know, you don't even need a wisp for this whole thing to work. Just use a trigger to check whenever a unit is selected, and establish that unit as the chosen race. There are some interesting variations of this concept that let you receive info on a race before actually choosing it - for instance, clicking on the unit corresponding to a race will give info on that race and store the unit's ID in a global variable. You could then click on a central unit, unrelated to any race, that acted as an "ok" button.
I've even made an UI that uses "slider bars" based on this concept, where you have a row of watchtowers, and clicking on a watchtower will cause all watchtowers up to that point to turn red. This is really useful when making difficulty bars, and for big menus where a dialog just doesn't work quickly enough. | 
Progress Bar
Events
Player - Player 1 (Red) types a chat message containing -random as An exact match
Conditions
Actions
Set random = (Random integer number between 1 and 4)
If (All Conditions are True) then do (Then Actions) else do (Else Actions)
-------- Race 1 Init actions --------