I have to collect what?

So when Legacy was sick, I took her to the Doctor a couple times. On my last visit the Doctor said he wanted a 'Stool' sample. Well that night I went home and tried to get one. Here are the steps: You need to Line the Diaper with clear plastic wrap and collect a fresh clean sample. Now the first question that popped out of my mouth was, so how do I get a sample if her poo is runny. The nurse said it may take me a couple times but I would get it. Needless to say she pooped on my floor, all over her clothes etc.. what a nightmare. But the next morning it looked like she was getting better. So I thought if she does well all weekend then I won't take a sample in. Today she regressed, so I tried to get a sample. I finally called and asked how I could get one cause all the clear plastic wrap was doing was getting stuck in her crack. The nurse laughed and said try getting those Gerber Vinyl pants. So we did, and guess what she didn't poo again. I am killing myself, should I just keep her naked and hold the cup under her butt till she has to go. Come on people there has to be a better way. Oh well I will try again tomorrow. I didn't think it would be this hard.