semibluff vs unknown 10/20

[helpmeout]

Party Poker 10/20 Hold'em (6 max, 6 handed) converter

Preflop: Hero is BB with Q[img]/images/graemlins/diamond.gif[/img], 9[img]/images/graemlins/diamond.gif[/img].
<font color="#CC3333">UTG raises</font>, MP calls, <font color="#666666">3 folds</font>, Hero calls.

Flop: (6.50 SB) 7[img]/images/graemlins/diamond.gif[/img], 4[img]/images/graemlins/spade.gif[/img], 7[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
Hero checks, <font color="#CC3333">UTG bets</font>, MP folds, Hero calls.

Turn: (4.25 BB) 2[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">UTG bets</font>, <font color="#CC3333">Hero raises</font>,

This is dumb isnt it? The guy will likely calldown with an Ace or a PP. So when should I make this play? vs a CO or button raise?

Or not at all because he will likely call with overcards?

I guess I just answered my own question but might as well get some thoughts.