how to compare values ​​labels?

Quick and easy, you basically use the programming language to do the sum for you and then compare the sum from the script to the sum on screen.  Here's a quick and dirty function I wrote in JScript

function TestValues(Value1, Value2, Total)
{
    var TestTotal = aqConvert.VarToFloat(Value1) + aqConvert.VarToFloat(Value2);
    if (TestTotal == Total)
    {
        Log.Message('The Total on screen is correct');
    }
    else 
    {
        Log.Warning('The Total on screen is incorrect');    
    }
}