Hi - another Craftsman & Replacement Opener distress post...

Moved into a home with Craftsman 1/2 HP opener (Green Smart-Learn button) with no remotes. Purchased two universal Clicker devices (CLT1D) mfg by Chamberlain.

I can program one of the new remotes just fine, but when I try to program the second, it wipes out the code from the first (and vice versa).

Any ideas on how to overcome this problem and get both Clicker remotes working with the same garage opener??