Value Mapping: how to loop over a nested context in a adv. user function

Hello,

i have the following source structure:

<rec> (1:1)

<field1>aaa</field1> (1:1)

<field2>bbb</field2> (1:1)

<b><struc> <u>(1:unbounded)</u>

<name>myName</name>

<value>myValue</value>

</struc></b>

</rec>

Destination structure:

<rec> (1:1)

<field1>aaa</field1> (1:1)

<field2>bbb</field2> (1:1)

<b><field3>bbb</field2> (1:1)</b>

</rec>

In order to fill the destination field3 i have to loop over the input-structure struc.

My problem is, that i don't know how to get access to the name/value pair with a

extended user-defined function. Since each occurrence in struc i not a simple string but consists of 2 fields, i guess it is not enough simply to loop over input String Array.

Please help.