UDF to add context changes by taking reference of other queue

Hi,

I require help in writing a interesting UDF. We need to insert context changes in a queue at specific position taking into reference of contexts in other queue.

We have a queue with X no.of fields.
We have another field in source which has its own contexts. Based on the position of its contexts. We need to add context changes in the above queue.

Ex:
We have 2 fields <Field1> <Field2>
<Field1> Queue needs to be modified will be like
1
2
3
.
.
,
100

field2 queue.

A
B
<ContextChange>
C
<ContextChange>
D
<ContextChange>
etc

The expected output should be like
1
2
<ContextChange>
3
<ContextChange>
4
<ContextChange>
etc

How can we take another queues context changes as reference and add the same ?