Calculate Percentage in the main report, getting values from the subreport

I have 2 reports: Main report (let's call it 'Main'), Subreport (let's call it "Sub")

 

Report Main contains Sub report in detailed band. Below is the report structure:

 

Column A              Column B                     Column C

a1                             b1                                   c1

                                  b2                                   c2     

                                  Total1                             c1 + c2

                                  %Total                            Total1 / (c1 + c2 + c3 + c4)

a2                             b1                                    c3

                                  b2                                    c4

                                  Total2                              c3 + c4

                                   %Total                           Total2 / (c1 + c2 + c3 + c4)

 

I want to calculate %Total in main report. 

I have followed below steps : 

1. Created variable "sum at report level" in the main report which is c1 + c2 + c3 + c4 from subreport.

The value for this variable I am able to get it.

2. Created variable "sum at band level" in the main report which is Total1 or Total2 from subreport.

The value for this variable I am not getting it somehow. 

3. Created variable %Total in the main report which is sum at band level/sum at report level

The evaluation time of the text field where I am displaying the value of %Total is set to "Auto"

 

I am not getting correct percentage value. I have tried setting different evaluation time. Is it possible to reset the variable at band level? Or any other way to calculate percentage?