Is there an easy way to make the defaultValue of a column equal the results of another column or query?

$g->select_command = “SELECT * FROM tbl_job
INNER JOIN
(SELECT (MAX(job_number) + 1) AS max_job
FROM tbl_job) top_job
LEFT JOIN tbl_customer ON customer_id = fk_customer
LEFT JOIN tbl_proj_man ON fk_proj_id = proj_id
“;

$col = array();
$col[“title”] = “max_job”;
$col[“name”] = “max_job”;
$col[“width”] = “50”;
$col[“hidden”] = true;
$col[“editable”] = true;
$cols[] = $col;

$col = array();
$col[“title”] = “Job Number”;
$col[“name”] = “job_number”;
$col[“link”] = “addunit.php?job={job_id}”;
$col[“width”] = “50”;
$col[“hidden”] = false;
$col[“editable”] = true;
$col[“editrules”] = array(“required”=>true, “number”=>true, “minValue”=>1000, “maxValue”=>9999);
$col[“editoptions”][“defaultValue”] = “{max_job}”
$cols[] = $col;

I simply want to find the next job_number in the DB and make it the default value in the col job_number. Thanks in advance.