how to specify arguments for an item in the Dock

I have X11 installed, and I prefer xterm to the terminal program that comes with leopard. I also like my xterm to have a black background and white letters, which requires you to run the command with two arguments (xterm -fg white -bg black). I have a link to xterm in my Dock but I can't figure out for the life of me how to specify those arguments so when I click it my colors are the way I want. Anyone know?

Thanks in advance!