How to read multiple structure xls files in C#

I tried to read multiple formats salaryslips but there are huge formats in salaryslip

 

.This makes me to define different algorithm for group of salaryslip.

I want to read all formats in one programs .For this 

1. I created alias table 

2. Then Founded  personal inf from salaryslip .Which is extracted correctly.

3. Then I founded salaryheads which also extracted in percentage of 40 percentage.

     But as I given information that some salaryslips have different structure so I am not able to get data perfectly.Please anyone give me best solution for this 

 

Thanks