Is there some option I can change so that I can change sketch dimensions to zero?

I am working on a design that is in flux. Right now, it wouldbe really helpful, if I could change one of my sketch dimensions tozero. It will not let me. Are there any options that will allowthis? I really don't want to have to go into the sketch, get rid ofthe dimension, change my line to vertical and then in the next 10minutes find out that I need that dimension back and not equal tozero. Any suggestions?

Thanks,
Carrie
(Solidworks 2007)SolidworksSketching