I thought you could just insert a clear image between your text but as you can see in TH
IS word the colours won't match for everyone because of the way forum skins work.
If you do want to use that method use enter one or more
[ IMG ]http://lebutler.lunarpages.com/perm/clearspacer50x1.gif[ /IMG ] where you want spaces (remove the gaps I added around the IMG commands to make them work)
An alternative is to write some/all of the message in an image editor and post the picture instead of typing it into the forum.