User define functions in Mapping - Need help...

Question

I have the following Source structure
<root> (1...Unbounded)
  <field1>
  <field2>
  <field3>
</root>
and need to map this in
  <target>
      <fields1>
      <struct1>
         <field2>
       </struct1>
      <struct1>
         <field3>
      </struct1>
    </target>
i.e i need to create twice the struct1 one for each field (field2, field3) no matter how many rows I have...
Example:
<row>
   <f1>1.1
   <f2>1.2
   <f3>1.3
</row>
<row>
   <f1>2.1
   <f2>2.2
   <f3>2.3>
</row>
should result:
  <target>
       <f1>1.1
       <struct1>
           <f>1.2
       </struct1>
       <struct1>
          <f>1.3</f>
       </struct1>
  </target>
Please advide

Answer 1

Thanks for the answer. But the problem is that the target structure is a standard IDOC and can not be change to be more exact:
The target message has two fields
<row>
   GIDate
   DocDate
</row>
and need to create two segments of the idoc  SHP_IBDLV_CONFIRM_DECENTRAL.SHP_IBDLV_CONFIRM_DECENTRAL02
for segment E1BPDLVDEADLN where TIMETYPE and TIMESTAMP_UTC changes based on the two flat fields of the row structure:
e.g.
if I have
<row>
  <deliveryNo>1111111111
  <GIdate>20070909</gidate>
  <DocDate>20071010</DocDate>
</row>
in the Idoc I neew to have
<E1BPDLVDEADLN>
<DELIV_NUM>1111111111
<TIMETYPE>WSHDRWADTI
   <TIMESTAMP_UTC>20070909
</E1BPDLVDEADLN>
<E1BPDLVDEADLN>
  <DELIV_NUM>1111111111
  <TIMETYPE>WSHDRLFDAT
   <TIMESTAMP_UTC>20071010
</E1BPDLVDEADLN>
I hope this is more clear...