Hello Chris,
Apologies for the delayed answer.
You can easily do this job on the client-side like so:
var rows = $find("WebDataGrid1").get_rows();
var rowsLength = rows.get_length();
for (var i = 0; i < rowsLength; i++) {
var row = rows.get_row(i);
var cell = row.get_cellByColumnKey("TemplateField_Status");
var cellElement = cell.get_element();
$(cellElement).find("input[value='Complete']").prop("checked", true);
}
I am attaching a working sample in case you need it.
Please let me know if you need anything else.