You can place the below syntax in the Calculcate event of the TOTAL field on your form.
Language : FormCalc
SUM(T2,T3,T4); (OR)
SUM(T2.rawValue,T3.rawValue,T4.rawValue);
Assuming your field names are T2, T3 and T4.. rawValue is not mandatory in FormCalc to get the field value.
Thanks
Srini