To check the status of checkboxes in a GridView column on click of a button, you can use JavaScript to loop through the rows of the GridView and check the status of the checkboxes in each row.

Here is an example of how to do this:

function checkGridView() {
  var gridView = document.getElementById('<%= MyGridView.ClientID %>');
  var rows = gridView.getElementsByTagName('tr');
  
  for (var i = 0; i < rows.length; i++) {
    var cells = rows[i].getElementsByTagName('td');
    var checkbox = cells[1].getElementsByTagName('input')[0]; // Assumes checkbox is in second column

    if (checkbox.checked) {
      // Checkbox is checked, do something
    } else {
      // Checkbox is not checked, do something else
    }
  }
}

In the above example, the checkGridView() function is called when the button is clicked. The function retrieves the GridView using the document.getElementById() method, and then loops through each row of the GridView using the getElementsByTagName() method.

For each row, the function retrieves the second cell in the row (assuming that the checkbox is in the second column) and then retrieves the checkbox element using the getElementsByTagName() method again. The status of the checkbox is checked using the checked property, and then the appropriate action is taken based on the status of the checkbox.

You can modify this example to suit your specific requirements, such as checking multiple columns or performing different actions based on the status of the checkboxes.