Auto Display

Hello Everybody,
With the help pf active scaffold i have created 3
columns…lets say a,b,c.Now if enter the value in a and in b…then
automatically it should show result in c.
For e.g.
a = 5
b = 5
Then automatically the value in c should be displayed as 10.

Can u suggest me how should i proceed with the same.


Amit K.