Problem using DataGridViewCheckBoxColumn

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Hi,

I am having problem using "DataGridViewCheckBoxColumn" in my project.
The function dgvCheckBox_Clicked is called when CheckBox in DataGrid is
clicked ( checked or unchecked).
dgvCheckBox_Clicked is fired by CellContentClick event on datagrid.

//Form1.Designer.cs
this.dataGridView1.CellContentClick += new
System.Windows.Forms.DataGridViewCellEventHandler( this.dgvCheckBox_Clicked);

However, I am getting "NullReferenceException was unhandled" is raised when
I click the CheckBox. :(

Here is the function I am using for test:

//called on Event: dataGridView1.CellContentClick
private void dgvCheckBox_Clicked(object sender,
DataGridViewCellEventArgs e)
{

//skip while form load
if (e.RowIndex == -1)
return;

if (e.ColumnIndex == 2) //CheckBox is the 3rd Column in DataGrid
{
if
((bool)dataGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Value)
{
MessageBox.Show("Loaded");
}
else
MessageBox.Show("Unloaded");

}

I'll be really glad if someone can show me right direction.

thanks
Rojina