spermicides/diaphragm & NFP?

Is it possible to combine the use of spermicides with natural family planning? And is it possible to combine nfp with a diaphragm?

I was asked why I don't use a diaphragm during ovulation for contraception. Which would come with the needed spermicides. I know that spermicides nor diaphragms interfere with your cycle. I just expect that spermicide will give me trouble analyzing the cervical mucus. Also; the fact that a diaphragm needs to stay in place for several hours, does give me a feeling it would influence the observation at least the next day...

Since I'm not sure about the answer and seem unable to find it, I thought I just post the question here :)

RedRoses