Subtract Selection

function selMake(t,l,b,r,E,M) { //Top, Left, Bottom, Right, true = Elipse false=Rectangular?, Mode(0=select, 1=add, 2 = subs, 3 = inter)
    try{
    var desc1324 = new ActionDescriptor();
        var ref496 = new ActionReference();
        ref496.putProperty( cTID('Chnl'), cTID('fsel') );
    desc1324.putReference( cTID('null'), ref496 );
        var desc1325 = new ActionDescriptor();
        desc1325.putUnitDouble( cTID('Top '), cTID('#Pxl'), parseFloat(t) );
        desc1325.putUnitDouble( cTID('Left'), cTID('#Pxl'), parseFloat(l) );
        desc1325.putUnitDouble( cTID('Btom'), cTID('#Pxl'), parseFloat(b) );
        desc1325.putUnitDouble( cTID('Rght'), cTID('#Pxl'), parseFloat(r) );
       
    if (E) desc1324.putObject( cTID('T  '), cTID('Elps'), desc1325 );
    else desc1324.putObject( cTID('T  '), cTID('Rctn'), desc1325 );
   
    desc1324.putBoolean( cTID('AntA'), true );
   
    switch(M){
        case 0:{
            executeAction( cTID('setd'), desc1324, DialogModes.NO );
            break;
            }
        case 1:{
            executeAction( cTID('AddT'), desc1324, DialogModes.NO );
            break;
            }
        case 2:{
            executeAction( cTID('SbtF'), desc1324, DialogModes.NO );
            break;
            }
        case 3:{
            executeAction( cTID('IntW'), desc1324, DialogModes.NO );
            break;
            }
        default:
        break;
           
        }   
    }catch(er){}
};
function cTID(s) { return app.charIDToTypeID(s); };
function sTID(s) { return app.stringIDToTypeID(s); };
function cTT(v) {return charIDToTypeID(v)};
function sTT(v) {return stringIDToTypeID(v)}
var h = app.activeDocument.height
var w = app.activeDocument.width
selMake((h*0.6),0,h,w,false,2)