I have done this for another purpose. You need two UDFs, one for the BELNR, one for the QUANTITY.

In my samples the parameters are named different, but I hope the principle is clear. You can just change the parameter names to your needs.

first: input parameter = taxCode

Vector taxCodeVector = new Vector();
for (int i = 0; i < taxCode.length; i++ ){
   if (!taxCodeVector.contains(taxCode<i>)){
      taxCodeVector.addElement(taxCode<i>);
      result.addValue(taxCode<i>);
   }  
}

second: input parameter = taxCode, amount

Vector taxCodeVector = new Vector();
Vector amountVector = new Vector();
// create vector from input array
for (int i = 0; i < taxCode.length; i++ ){
  int vectorIndex = taxCodeVector.indexOf(taxCode<i>);
// if tax code not in vector so far
   if (vectorIndex == -1){
// add tax code and amount to vecors
      taxCodeVector.addElement(taxCode<i>);
      amountVector.addElement(new BigDecimal(amount<i>));
   }  else {
// add the amount to the vector element corresponding to tax code
     BigDecimal currentAmount = (BigDecimal) amountVector.get(vectorIndex);
     amountVector.set(vectorIndex,currentAmount.add(new BigDecimal(amount<i>)));
   }
}
// output amount values
for (int i = 0; i < amountVector.size(); i++ ){
  result.addValue( ((BigDecimal) amountVector.get(i)).toString());
}

the UDFs are of type "value of a context", but you have to set the context if the incoming parameters to the highest level, so there is only one context.

Edited by: Stefan Grube on May 12, 2010 9:39 AM