Special price in combinations

[stdio]

Hi,

I created some combinations on my shop and I would like to have a special discounted price for one of my combination. For example I have these combinations:

Product 1 = $10
Product 2 = $20
Product 3 = $15 <-- this should display "On sale" message

Currently all the combinations are displaying to "On sale" message and I only want combination #3.

Is this possible? Can anyone advise me how to achieve it?

Thank you!