Problem Related Html Table Merge cell down(column wise)

Need a help in other problem ...

Actually i have to merge down column wise..in a table (html table)

I have done all coding part but it shows exception in some cases when i have merged a column cells and again then when i merge other column next to it then it shows error index not available

I have attached code please check its logical structure and if any change needed please correct it and let me know .

Would be a great help......

	Works good here

But when we merge 1 and 2 or 3&4 or 3&4&5 so on ...it shows error of index