Error while accessing this.URL

Question

I got the following error while trying to access this.URL:
"NotAllowedError: Security settings prevent access to this property or method."
with javascript code:
try{
    var x = this.URL;
    app.alert(x.toString().substr(1,2));
}catch(e){
    app.alert('Error during submit.\r\n' + e);
but the documentation said I should have Read access.
http://livedocs.adobe.com/acrobat_sdk/10/Acrobat10_HTMLHelp/wwhelp/wwhimpl/common/html/wwh elp.htm?context=Acrobat10_SDK_HTMLHelp&file=JS_API_AcroJS.88.421.html

Answer 1

Code is located in a Button Mouse Up event (Run javascript). Version is Acrobat 10 Pro for Windows 7 32bit.