How do we implement the select all functionality for checkbox group which is similar to the selmodel checkbox in Grid @extjs

Might sound easy but I am stuck at Select all and deselect all functionality for CheckboxGroup.

For now I have the select all and deselect all working with setValue(true/false) function in ExtJs

But I also need to implement deselect the "select all" checkbox when I deselect any value from the checkbox group, when "select all" is previously selected.

How do we bind both the checkbox and checkbox group for this functionality?

can we include selModel in checkboxGroup?

any ideas?