Use DataGridView CheckBox Column for a string data column

I have this table in database:

applicant  |  module  |  date  |  approvation  | 
  xxxx         xxxx      xxxx        xxxxxxx
  yyyy         yyyy      yyyy        yyyyyyy
  tttt         tttt      tttt        ttttttt

I have this db table. After query I assign DataTable to my DataGridView.DataSource:

QueryAssist qa = new QueryAssist();
DataTable dt = new DataTable();
dt = qa.runQuery('myquery');

dgvApprovazione.DataSource = dt;
dgvApprovazione.AutoResizeColumns(DataGridViewAutoSizeColumnsMode.DisplayedCells);

// modify, transform 2nd column in cellLink
foreach (DataGridViewRow row in dgvApprovazione.Rows)
{
    row.Cells[1] = new DataGridViewLinkCell();
}

Now I want to transform column approvation that is a string approved or not approved and show a check box instead.

if value of this cell is approved check box is checked and not modified (onlyread).

something similar:

foreach (DataGridViewRow row in dgvApprovazione.Rows)
{
    if (row.Cells[3].Value.ToString().Equals("APPROVED"))
    {
        row.Cells[3] = new DataGridViewCheckBoxCell();
    }
} 

I have a problem to implement ... help me.

It's possible ? How?

recapping:

I want to change a column that value contain is a text/string (approved or not approved ) in checkbox (checked or unchecked)

Sorry for bad english ..

Good alternatives?