[SOLVED] Scaling transition

This may be a bit of a newb question, but that's because I'm a newb.
I know I can change the scale/size of an object using the "Modify the scale of the specified object" action. But the scaling occurs instantly. How do I add a transition to the scaling, that you can visually see the object changing in size? For example, the player collects a coin, and a sphere object somewhere in the scene gets 20% bigger during a time of three seconds?
I know I can change the scale/size of an object using the "Modify the scale of the specified object" action. But the scaling occurs instantly. How do I add a transition to the scaling, that you can visually see the object changing in size? For example, the player collects a coin, and a sphere object somewhere in the scene gets 20% bigger during a time of three seconds?