I need to place constraints on a length of metal panel and I can not for the life of me create a parameter that will work. What I need the parameter to do is the Length of the Panel can be as long as 30'-0" and as small as 1'-6" but I can not make it so that if the panel is say fifteen that it will stay that way. What am I doing wrong? Or am I using the wrong parameters I usually use dimensions and constraints so. I think I have tried hundreds of formulas and none of them work.