check cells

Hello,

In my worksheet i need to check cells to make sure they have data before the next range can accept data.

Example.

I want to make sure range N4:Q11 has data in each cell before range P15:Q18 can accept data.

If range N4:Q11 has all data and P15:Q18 starts accepting data and if someone decides to clear any data from first range
i would like excel to stop them.

I would appreciate any help with this.

Thanks.