bathroom controll issues

Question
My 14 mo gsd has control issues over going to the bathroom. she will only go at home or at my office.  This is an issue as she is training to be a service dog for my 18 yr old son and is out and about with him constantly.  She is great in all other areas except this one.  How do you convince a dog that you know needs to go, to go where she is rather than having to leave where you are to take her to her one spot?  She will hold it for HOURS which we know is not good for her and make every one miserable in the process.

Answer
Yes I understand the problem.  Training them to go on command wherever they are works better when they are younger and can't hold it as long.  When you have a block of time and she is due to go, start walking.  Exercise stimulates the body to eliminate.  Walk however long it takes stopping to give her a chance in likely places.  Take some water along and let her drink if she wants to.  Eventually, she will have to go.  When she does, lavish praise on her.  You may have to keep doing it, walking in different places.  Try to restrict her chances to use the ''right'' areas at home and work.  When she shows a need to go out, don't let her use the regular area.  Walk her elsewhere.  

If you are working with a school or trainer, they may know some tricks I don't.