Jeff,
I'm not exactly sure of what you are trying to do. Is it possible you could post your code, or a screen shot of the diagram in question, so that I can get a better understanding, and possibly offer some assistance?
I am familiar with hex files, but not with the : marker separating records. This may be able to be solved with simple text parsing, and as I am not familiar with how you are retrieving and/or displaying the files, I require more information.
Thanks