Tearing my hair out... Please help... Rollover/SwapImage problem

Good afternoon everyone. Please if anyone can help me i would really really
appreciate it. I am beyond frustrated at the moment. Here's what i'm trying to
do: On the right i have 10 buttons to show images in my portfolio. I have a
rollover for each of the buttons. When i rollover the button it changes to the
rollover state and when i rollout it goes back to the original button. I have
also got an image on the page called replace.gif and I have given it an
instance name 'replace'. What i want is that when i click on the first button
it changes the 'replace.gif' to logo1.gif and keeps the button on his
downstate. Then when i click on any of the other buttons it will change it
back to the original state. Does that make sense? At the moment when I
rollover the button it works but when i click it, it changes 'replace' to the
logo1.gif and when i roll off it it changes logo1.gif back to 'replace'.
Thanks :-)