while displaying the record

 I had used the "Running total" for that.

 

But to Display in a proper format, I had done some manipulation

 

//******************************************************************************
// Prints the cumulative value of the RunningTotal variable
// for {AS_INTEREST_TYPES_TL.INTEREST_TYPE}
//******************************************************************************
WhilePrintingRecords; 
StringVar RunningTotal;
RIGHT((RunningTotal),LEN(RunningTotal)-1);

 

But because of the last line[RIGHT((RunningTotal),LEN(RunningTotal)-1);]

its showing an error while running the report.The error is

"string length is less than 0 or not an Integer"

Can anybody help me on that ?