Help with gene model diagram

Hi,
We think Nodebox is really cool, but we can't seem to get it to do what we want (make gene models) in a way we are happy with.
We have been able to make something very similar in Nodebox using maths (to render groups of a shape and then group these together) rather than converting values into symbols, but it should be simpler...
We can do everything needed except get a string containing 'aaabbbaaabbaaa' to replace the 'a's with one shape and the 'b's with another (along a line/path).
Our apologies for asking you to do support for us, but we are both really keen to use Nodebox and share methods.
A copy of the illustration we are trying to duplicate is attached - it was made in InDesign using a find and replace function.
Best wishes,
Tim Holmes
Roy Storey

Hello Tim, Roy,

Here is a way to do it. As you will notice my strings are for the moment cut into separate characters divided by a semicolon. The strings themselves by a comma. In the subnetwork each string is processed and each character gets it shape. The zip_map node is the key here.
In the next release there is a "characters" node that will make the above work alot easier since it will split each string into its characters. Anyway, I attached a sample file, which will be obsolete for a big part with the next release,

regards,

Lucas