You can do the same kind of thing. Here is a snippet that shows how to get at the GridListControl object so you can work directly with it in CurrentCellShowingDropDown.
private void gridControl1_CurrentCellShowingDropDown(object sender, GridCurrentCellShowingDropDownEventArgs e)
{
GridCurrentCell cc = this.gridControl1.CurrentCell;
//the cell 2, 4 is where I want to hide coulmn 1
if(cc.ColIndex == 2 && cc.RowIndex == 4)
{
GridDropDownGridListControlCellRenderer cr = (GridDropDownGridListControlCellRenderer) cc.Renderer;
GridListControl glc = cr.ListControlPart;
glc.Grid.Cols.Hidden[1] = true;
}
}