Help for GIRLS taking piss tests

I dont know if this will work for EVERYONE...sence situations and circumstances may be different but I'm on Probation..and i've been on it for about 4 years now. I've done drug tests about every two weeks....I occasionally get high maybe once or twice a month and one think i do if i do it alittle to close to my piss test....I SAY IM ON MY PERIOD....my probation just sends me off and tells me to come back next week. She has asked to see "proof" lol.....maxi pad and food coloring solves that. Some may not be comfortable with trying this, but it can be used as a last resort, althought it may not work for everyone....just thought i might try and help someone out...