Detecting specific text in cell to activate functions

Hi to all,

I have a form in which there is a field which has a few hundred specs for conducting inspections. They run in a sequence of values from "M1XXX rev. X" to "M4XXX rev. X" in cell N10. I'm trying to hide lines 513 to 538 whenever "M3XXX rev.X" to "M4XXX rev. X". I already have part of the form that is already hiding some of the rows and columns but i'm absolutely cluless on how to write the codes to detect just M3 and M4 in the value that appears in cell N10 to hide the lines. Can anyone help?

Here is the form:
testing_form.xlsm

Thanks.

Regards,
Ayub

Thanks for the tip, i will try it out. Can i just verify if i can use the formulas in macros?

Thanks.