PI Mapping Issue

Hi

How can i do the below mapping? We need to add the segments..Based on Field2   ("A")

Input:

-------

<Row>

  <Segment1>

     <Field1> 100 <Field1>

      <Field2> A <Field2>

     <Field3> XYZ <Field3> 

   </Segemnt1>

<Segment2>

     <Field1> 50 </Field1>

    <Field2> A </Field2>

     <Field3> XYZ <Field3>

</Segemnt2>

<Segment3>

    <Field1> 50 </Field1>

    <Field2> B </Field2>

     <Field3> XXX <Field3>

</Segemnt3>

</Row>

Output:

----------

<Row>

  <Segment1>

     <Field1> 150 <Field1>

     <Field2> A <Field2>  

     <Field3> XYZ <Field3>

  </Segemnt1>

<Segment3>

    <Field1> 50 </Field1>

    <Field2> B </Field2>

     <Field3> XXX <Field3>

</Segemnt3>

</Row>

Thanks,

Krishna.