Extjs 3 - Grid grouping with a checkbox

Question

I have a grid configured with a GroupingStore, GroupingView and a CheckColumn that displays grouping data using extjs 3.The data that I display in grid is list of students as rows and subjects as headers. I will group all students that fall into each section and display under each group. Each cell in grid is a check box(used Ext.grid.CheckColumn) that will be checked if user pass in that subject else not checked. The admin will have to check/uncheck all the boxes and generate the report as per the marks scored by students. I want to provide an extra check box in group header per each subject so that if admin checks that cell, all checkboxes under that column(in that group) will be checked automatically. My qns seems similar to Checkbox for group header of extjs grouping grid. It talks about only 1 check box per group rather than multiple checkboxes for a group(i.e one per each column).... Any thoughts ???