Returning Variable From Within Nested Function

The code is below but basically I have two global variables, then I have a function and then a function within that, I am simply trying to update these global variables from within the nested function so i can then go on and use them in another function! this sounds like quite a straight forward request to me, but maybe it can not be done? When I do an alert on the variables (after I have apparently updated their values) I get 'undefined'!

Code JavaScript:
var resultLatB;
var resultLngB;
function getLatLngFromTown(town, callbackFunction) {
var localSearchB = new GlocalSearch();
localSearchB.setSearchCompleteCallback(null,
function() {
if (localSearchB.results[0]){
resultLatB = localSearchB.results[0].lat;
resultLngB = localSearchB.results[0].lng;
pointA = resultLatB;
pointB = resultLngB;

//THIS WORKS
alert("Test 1 = " + resultLatB);
alert("Test 1 = " + resultLngB);
}});
localSearchB.execute(town + ", UK");
//DOESN'T WORK... SHOULD IT?
alert("Test 2 = " + resultLatB);
alert("Test 2 = " + resultLngB);
}
getLatLngFromTown("oxfordshire",null);

//I WANT THIS TO WORK!
alert("Test 3 = " + resultLatB);
alert("Test 3 = " + resultLngB);