How to Group on a Column which has type combo?


I have a grid with 4 columns. The first 3 columns are of type combo. The 4th column is of type ron.

I want to Group on the first column. When I try that it shows the Value in the Column rather than the Text in the Combo box as the Group Header row. So I tried :
grid.customGroupFormat=function(name,count){return cmbFirsCol.getComboText();}

However that produced nothing in the Group Header row. I’ve seen the :

grid.forEachRowInGroup(name,function(id){ do something with row (id)}

But I can’t understand how to use it. Please can you tell me how I can get the combo Text to appear in the Group Header Row.