I am not sure of your reason for doing this, but this work around might work for you.
Go into Messages and press Alt + P, this will show your entire call log.
From there, press the menu key and select Search
Leave all fields as blank/default but the last 2. Make them as follows.
Show: Sent Only
Then press the menu key and select search. This will show all of your placed calls. From here, you can press T to go to the top, then press the Menu Key, and select Delete Prior. This will delete all of your outgoing calls.
__________________ The difference between stupidity and genius is that genius has its limits. When you take things for granted, the things you are granted, get taken. Even a mosquito doesn't get a pat on the back until it starts to work. Too many people miss the silver lining because they're expecting gold. [BES 5.0.3 / GroupWise 2012 HP2]