If cells are empty in a row then show "Error"

Hey experts!

I am from India and would really appreciate if anyone could help me out.

I have attached the screenshot of my excel file.

So i enter the product code in Range B11:B24 and i get the other relavant details except the Amount Column as prices are different for different customers.

I manually enter the amount .

I was looking for something through which if a user misses out on the amount column then Q36 shows "error"

Because many a times I have forgotten to type the amount.


Example :

I have filled In B11, B12 an B13 with codes.
However i enter the amount of only B12 and B13.
Thus, I want it to show error in Q36 because i have missed out on entering amount of B11


Please help me out.

Thank You