removing duplicate values from a queu in graphical mapping

Hi,

Can i remove duplicate values from a queu, but still keep the existing context changes?

Is it possible with graphical mapping (node functions) to go from this queue

<null>
[aaaa]
[aaaa]
[aaaa]
[aaaa]
[bbbb]
[bbbb]
[bbbb]
[contextchange]
[cccc]
[cccc]
[dddd]
[dddd]
[dddd]
[dddd]
[contextchange]
[eeee]
[eeee]
END OF QUEUE

to this queu:

<null>
[aaaa]
[bbbb]
[contextchange]
[cccc]
[dddd]
[contextchange]
[eeee]
END OF QUEUE

The number of times that a value occurs is variable, as is the number of values within a context, as is the number of context changes in the queue.

So, once more, question is how to remove the duplicates while keeping the context changes as they are.

Thx for advice

Kr

Robert