It's definitely something you want to talk to your GSTL or ELT-GE about. I've found that most stores are more than willing to work with a person (as far as availability) especially if it is a person who they think can go forward in the company. In fact, even if you aren't looking to continue in the company, go to them and say:
" I'm really looking to advance in Target and I want to be a GSA. However, I have scheduling issues right now and was wondering, if I apply for the open GSA position, is there any way it can be worked around? "The scheduling issues would only be until _____ and then I would have full availability."