Creating Email alert based on % of target value

Hi All

I am trying to create an email alert that is based on a user defined % of a target value from a service calculation:

var CurrentTime = new Date();
var Midnight = new Date();
Midnight.setHours(0,0,0,1);
var params = {
oldestFirst: true /* BOOLEAN */,
maxItems: undefined /* NUMBER */,
sourceTags: undefined /* TAGS */,
endDate: CurrentTime /* DATETIME */,
query: undefined /* QUERY */,
source: source /* STRING */,
startDate: Midnight /* DATETIME */,
tags: undefined /* TAGS */
};
// result: INFOTABLE
var result = Things["ApexReadingsStream"].QueryStreamEntriesWithData(params);
var newField = new Object();
newField.name = "Difference";
newField.baseType = 'NUMBER';
result.AddField(newField);
var tableLength = result.rows.length;
for (var x = 0; x < tableLength - 1; x++) {
    var newerRow = result.rows[x +1]
    var olderRow = result.rows;
    //row.Difference = row.Value-result.rows[x-1].Value;
    newerRow.Difference = (newerRow.Value-olderRow.Value) * 1000 ;
}

I am struggling to understand the concept of how to achieve this in thingworx?

Any suggestions from anyone...

Thanks

Darryl