2 Pop Up Windows only if 2nd exists

[phpbeginner]

<SCRIPT LANGUAGE="JavaScript">
<!-- Begin
function popUp(URL,URL2) {
day = new Date();
id = day.getTime();
eval("page" + id + " = window.open(URL,'" + id + "', 'toolbar=0,scrollbars=1,location=0,top=10,left=10,statusbar=0,menubar=0,resizable=0,width=408,height=400');");

day = new Date();
id = day.getTime();
eval("page" + id + " = window.open(URL2,'" + id + "', 'toolbar=0,scrollbars=1,location=0,top=10,left=450,statusbar=0,menubar=0,resizable=0,width=408,height=400');");
}
// End -->
</script>

I have a map which shows sales people by location and if more then one sales person exists then I would need 2 pop up windows.

 

This works great other than the fact that the areas with one sales person are getting a blank 2nd popup as a second salesperson does not exist.

 

Any help would be appreciated.

 

Thanks In Advance