Change font size dynamically google maps-InfoBox

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Javascript

Google-Maps

I want to change the text size of a label which I have created by InfoBox in google maps. It is affecting the text but not text size. Here, what I have tried so far:

function addLabel(text,a,fontSize){
fontSz = fontSize + "pt";
            var myOptions = {
                 content: text
                ,boxStyle: {
                   border: "0px solid black "
                  ,textAlign: "center"
                  ,fontSize: fontSz
                  ,width: "50px"
                 }
                ,disableAutoPan: true
                ,pixelOffset: new google.maps.Size(-25, 0)
                ,position: a
                ,closeBoxURL: ""
                ,isHidden: false
                ,pane: "mapPane"
                ,enableEventPropagation: true
            };

            var ibLabel = new InfoBox(myOptions);
            ibLabel.open(map);
            return ibLabel;
    }

Here I call it inside a function..

if(label.length > 0){
            for( var j=0;j<xx.length;j++){
                label[j].setVisible(vis);
            }

        }else{//create and add new ones
            for( var j=0;j< xx.length;j++){
            alert(map.getZoom()+5);
                label[j] = addLabel(j+radars[j][1],new google.maps.LatLng(xx[j][2], xx[j][3]), map.getZoom()+5);
            }
        }

But the font size is not changing dynamically, Can somebody please help me?