How do I set the value of a checkbox in a datagrid from vbnet code behind?

I have a modal window containing a datgrid with three checkboxes. One is the "selected" checkbox. Two are user editable. I need to set the two user checkboxes to true or false based on data entered. Databinding works fine, but later in the code I cannot find a way to check or uncheck the boxes. I can set their text to "true" or "false" but the datagrid then shows "true" or "false" instead of a checkmark. I've been beating my head on this for days now...any ideas? Surely someone has had the same need....

I've been trying all sorts of code to reference the checkbox cells and can see if they are checked on unchecked but the same sort of references do not work when trying to set the value. I really don't have any code to post because it has all been scrap.