How do I keep black hair dye out of my blonde hair while dyeing it?

I have black hair with blonde bangs, and I need to find a way to keep my black dye from getting into the blonde when i rinse it out. Otherwise, my blonde turns an ugly color for about a week. Any tips??How do I keep black hair dye out of my blonde hair while dyeing it?
you could try tying your bangs together, like with braids or in a little pony tail, that might work.How do I keep black hair dye out of my blonde hair while dyeing it?
I agree with Andi