Dermination of the period of a signal

Hallo everyone, i would like to find the period of a signal whose the frequency changes over the time. I have an idea how to do it. By measuring the time corresponding to two consecutives peaks values of the signal. the difference of the both times correspond to the period. I want to implement it in Simulink, not in Matlab. i dont know which block i should use. any idea?? it is very urgent!!

Thanks in Advance

[Jan]

I do not even know, what "frequency changes over time" explicitly means.

The word "urgent" occurs usually in questions, which does not contain enough details to be answered. Therefore many users of this forum skip questions, which contain "urgent". See also: https://www.mathworks.com/matlabcentral/answers/29922-why-your-question-is-not-urgent-or-an-emergency

[Franck Joel Simo]

i have attached above one example of a signal whose the frequency changes over time.

[Jan]

Then what is the wanted output for this input? Can you mark the zones manually, because it is 1 data set only, or do you need an automatic separation, because you have to process thousands of signals?

Do you see it? There is a high correlation between questions containing the term "urgent" and the demand for questions for clarifications, which take at least several days.