How to get combo boxes available differently

I have grid which has combo box in each row of grid I want to remove some of the values loaded.
but problem is am getting combo object but I couldn’t get keys.but remove works with
Whole combo related events but I want to do this for each of the rows

This works

but my case is

row 1 1,new (here no 1 is selected)

row 2 2,old (here no 2 is selected)

finally I want to remove only changed from all the 3 option from combo.I tried below code please hlep to solve using DHTMLX 3.5.

      var allRows = gridControl.getAllRowIds(',');
       var rowArr = allRows.split(',');
       for(i = 0; i < rowArr.length ;i++)
               var combo = gridControl.cells(rowArr[i],7);

If you need a collection to be specific for a cell you need to use the following api method:

combo = grid.getCustomCombo(rId,cIndex)