Hi TrueSugar
I think you can put your challenges in your signature, then they will show each time you post.
(for example - myfitnesspal weightloss ticker at the bottom of this post is part of my signature, it comes up each time i post)
Click on User CP, this takes you to Your Control Panel,
In the User Control Panel, there are headings along the left side of the page. One of the headings is -Options & Settings, under this heading there is an option to edit signature. This is where you can list the challenges.
Hope this helps