In the "Trade Link Script Syntax" add in:
tp/out.php?p=60&fc=1&link=gal&url=
This will send 60% of the clicks to content and 40% to trades, you are able to change the number '60' to whichever number you wish. If you change it to 50, it means 50% of the clicks get to the content and 50% get sent to trades.