Return value is not returning value- Pls help

[tanvirtonu1]

This is what I did to get return value from sub report-

1.Add a varible (e.g. - val), and setting calculation Type- System

2.In sub report properties of master report, in Return Values Box, add sub report variable ( e.g- subval) and destination variable as created above- val .

3.Add variable ( subVal ) in sub report design properties and set a string (e.g. "Return this Value") in variable expression.

4.Add a textfield ( setting $V{val} as expression) in main report to show the content of return variable from subreport.

NB. All variables are of type- String

Yet, I cant see the string( "Return this Value")  which is returned from sub report through" subVal " into the variable- " val "

Is there anything missing in my process? PLS help

One more thing when should I use "System" as calculation Type.