Dodge Ram Running Boards

Please Help. I'm Trying To Wire Some Aftermarket Lighted Running Boards Into My 2005 Dodge Ram 1500. I Would Like Them To Come On When The Cargo Lights Come On. It Seems Impossible To Tie Directly Into Those Wires. I'm Hoping To Locate Something Under The Hood.

look for the switch in the door jam, that allows the inside lites to com on when the door is opened and wire to it