Excel file filled fields number

I have overnight generated excel report files with over 20000 rows and 45 columns, 11 of this columns are containing numerical values. I want to check is the number of filled in cells higher or equal 1, we had a problem once when these columns where generated empty.

Right now we do it manually by selecting the 11 columns and 20000 rows and checking the number of the ones that are filled it gives us 95000. Then we take this number and do simple mathematical 95000/20000 that gives us 4,7 filled fields average which is good.

Is it possible to perform such check during or after file generation with junit test, and throw a log/email message when the number is lower or equal 1?

I'm new to Java and excel files testing topic.