Dividing a coulmn into two..

[learner]

Hi,
I want to create a List grid coulmn, where one column will cosist of two sub - coulms, the exact structure should as like the attachment.
Can anybody plz help how to achive this?
Using header span i can achive first level of my requirement but not able do completely, as i sub coulmn also hav sub coulmn again.

[wwwhe]

check headerSpan

[learner]

check headerSpan

Please chek the attached image, using header span i can using first level, again if i want to make sub-column of a sub-column , i can't able to do