Is there a way to lock a column via js or xml or both?
What do you mean by “lock” column?
If you want to lock column position - you can use split mode
    dhtmlx.com/docs/products/dhtmlxG … 7300245000
If you want to lock edit operations for column, it can be done with next code
    mygrid.attachEvent(“onEditCell”,function(stage,id,ind){
        if (ind==SOME)
            return false;
        return true;
    });
where SOME - index of column in question.