You need to be more specific. AM? FM? Are you referring to % of modulation in AM? Modulation index in FM? Incidentally, there are a lot of other modulation schemes that are based on and similar to AM and FM. Referring to one of these?
Then there is no relationship between the two. 100% modulation at a modulating frequency of 100 Hz is the same as 100% modulation at 1000 Hz. All it does is move the sidebands from 100 Hz away from the carrier to 1000 Hz away from the carrier. Changing the modulating frequency will not change the percentage of modulation.