I am attaching a sample that does a similar functionality, with the check boxes displayed in the header.

In the sample provided I am creatimg to templated columns and assigning checkboxes at the header. In the InitilaizeLayout event I am checking/unchecking the CheckBoxes at the header according to the values in the first row using the following code snippet:

     if (e.Row.Index == 0)
        {
            e.Row.Hidden = true;

            foreach (UltraGridCell cell in e.Row.Cells)
            {
                TemplatedColumn tc = cell.Column as TemplatedColumn;
                HeaderItem item = tc.HeaderItem as HeaderItem;
                CheckBox checkbox1 = item.Controls[1] as CheckBox;

                checkbox1.Checked = ((int) cell.Value) != 0;
            }
   

            
       
        }

On the client side I attached an event when the checkbox is fired.  First I check the column that was checked, and I get the first row in the Grid and I assign it the value using the following code snippet:

function HeaderCheckedChanged(sender){
    var grid = igtbl_getGridById("<%= UltraWebGrid1.ClientID %>");
    var column = igtbl_getColumnById(sender.parentElement.id);

    if (column == null)
    {
        alert("Debugging: Column is null");
        return;
    }
   
   var index = column.Index;
   
   
    myrow = gridID.Rows.getRow(0);
var cell_value = myrow.getCell(index).getValue();

if((cell_value) == 0)
         {
          myrow.getCell(index).setValue(1);
          }
    else
          myrow.getCell(index).setValue(0);     
         
   

}

Magued