condition of amounts in a column of report output in oracle GL

 Hello,

I have created a report in  xml template and registered in oracle apps.i have created a rdf report which is showing two column values in output.the following requirement as follows? 

First condition:

There are tow columns A and B.If column A having amount 100 and column B is 20.The requirement is to show amount in Column B is A+B(100+20)=120 while column A should be remain unchanged .i.e 100

2nd condition:

 if column A having 100 and B having 0 amount,then column B should be 0(no addition of column A) while column A should be remain unchanged .i.e 100