Succeed using computers? Pull the other one! (4,3,2)
I believe the answer is:
come off it
'pull the other one' is the definition.
(both are expressions of incredulity)
'succeed using computers?' is the wordplay.
'succeed' becomes 'come off' (I've seen this before).
'using computers?' becomes 'IT' (information technology).
'comeoff'+'it'='COME OFF IT!'
(Other definitions for come off it that I've seen before include "Don't be ridiculous!" , "get down from there" , "You're mad!" , "Stop being so stupid!" , "Don't make me laugh" .)