Change a column type to an checkbox

Hi there

I have a column in my DataTable that is called "checked"

I want to make this a checkbox.

With this code it is not changing it:

                GridViewCheckBoxColumn checkboxcolumn = new GridViewCheckBoxColumn();
                checkboxcolumn.DataType = typeof(int);
                checkboxcolumn.Name = "checked";
                checkboxcolumn.FieldName = "checked";
                checkboxcolumn.HeaderText = "Checked?";
                this.grdIssueAcceptance.MasterTemplate.Columns.Add(checkboxcolumn);

With this it added the type nicely, but it is another field. I do not want to ADD a field. 

                GridViewCheckBoxColumn checkboxcolumn = new GridViewCheckBoxColumn();
                checkboxcolumn.DataType = typeof(int);
                checkboxcolumn.Name = "checked02";
                checkboxcolumn.FieldName = "checked02";
                checkboxcolumn.HeaderText = "Checked?";
                this.grdIssueAcceptance.MasterTemplate.Columns.Add(checkboxcolumn);

Regards

Kobus