How to dynmically make a cell editable in jqGrid PHP

Question

I have a jqGrid PHP project where I have been able with the below code to make rows background color and editable = false, based on the value of a cell in that row.

$rowattr = <<<ROWATTR
function (rd) {   
    if (rd.br_re_ending == "OTFN") {
        return { "style": "background-color:#FF9999; background-image:none;", "editable": false };
    }
}
ROWATTR;

$grid->setGridEvent('rowattr', $rowattr);

What I am now trying to do is to similarly use the value of a cell to determine if another cell in that same row should be editable or not. I have tried several options like the below, but with no avail.

$rowattr = <<<ROWATTR
function (rd) {   
    if (rd.br_ch_flag_extrameals == "STD") {
    return { "setColProp", "br_ch_ch2_mon", "editable": True };  
    }
}
ROWATTR;

$grid->setGridEvent('rowattr', $rowattr);

Can someone please provide some help or guidance in how to achieve this?

Thanks, Adri