Macro needed to compare multiple cells

I am new to Excel macros and am currently right now trying to write a macro that would highlight a row if a condition existed. The best way that I can I explain is it as follows:

If
cell M >= (90% of Cell N) and cell O >= (90% of Cell N)
then
Highlight the row

I have over 3400 rows and I have concluded that writing a macro would be the most efficient way. I am open to any suggestions. Thanks in advance