Data minus data(before year)

[n1ef5ng1]

Hi I need to find the difference of same month different year data.

i.e 2012 Feb value is 2000

     2011 feb value is 1300

Desired value is 700

Is there any ways I can work on this through expression? It will automatically calculate the difference of 3 years data without any user input.

This is my code

(Sum({<
Soldier_Class_Name = {'L'}
,Derived_Status = {'THIP'}
,Unlocode_Port_Of_Sleeping= {EE*'}
>} TEU)

/
Before( Sum({<
Soldier_Class_Name = {'L'}
,Derived_Status = {'THIP'}
,Unlocode_Port_Of_Sleeping= {'EE*'}
>} TEU) , 12)
*100))-100

However, it will display all the values even if it is null value ( i have checked surpress value etc)

Therefore my question is, is there any code i can use to substitute the code, before?

Thanks

[n1ef5ng1]

anybody....