My example uses a custom entity to lookup a post code. Place this code in the CustomContent of a screen which has a post code on and replace _Datasites__postcode with the field name of your postcode e.g. _Dataaddr_postcode. This will place three buttons on for Google, Streetmap and Bing Maps. Hopefully this will point you in the right direction : 

<input type="button" value="Google Map" name=Map1 onclick="LaunchMap(1,_Datasites__postcode)"/>
<input type="button" value="Streetmap" name=Map2 onclick="LaunchMap(2,_Datasites__postcode)"/>
<input type="button" value="Bing Maps" name=Map3 onclick="LaunchMap(3,_Datasites__postcode)"/>
function LaunchMap(mapindex, fieldobj) {


    var sitepostcode = fieldobj.outerText;

    var URL = '';


    if (sitepostcode != '') {


        switch (mapindex) {

            case 1:// google maps

                URL += "http://maps.google.co.uk/maps?f=d&hl=en";

                URL += "&saddr=RH13+5QH";

                URL += "&daddr=" + sitepostcode.replace(/ /, "+");

                URL += "&btnG=Search";

                break;

            case 2: // streetmap

                URL += "http://www.streetmap.co.uk/streetmap.dll?postcode2map?";

                URL += sitepostcode.replace(/ /, "+");

                break;

            case 3: // bing maps

                URL += "https://www.bing.com/maps?rtp=adr.RH13+5QH~adr.";

                URL += sitepostcode.replace(/ /, "+");

                break;

            default:

                window.alert('Incorrect Map index specified. Please speak to IT');

        }


        var win = window.open(URL, 'Locations', 'status=yes,toolbar=no, menubar=no, location=no,resizable=yes, scrollbars=yes');

        win.focus();

    }

    else {

        window.alert('No postcode to perform search with. Please ensure address has a postcode');

    }


}

Thank you fine sir!!!  This will at least get me going have a great rest of your week!