A Pronto Hex code starts like this.
0000 006D 00xx 00yy
The 0000 is a signature for Raw Code format. The 006D is the timing identifier. the 00xx is the number of one-shot pairs (in hexadecimal) of IR code data. The 00yy is the number of repeating pairs of IR code data. A pair is 2 sets of 4 digits with IR timing data. For example, 000F 0020
If you are so lucky to have a code that starts like this, it will repeat if button is pressed and held.
0000 006D 0000 0012
To make it be a one-shot code, simply change the locations of the counts.
0000 006D 0012 0000
While this may not be ideal, it often works, especially if you tinker with the IR Code duration.
For more info on what I just did or more background, you might want to see Barry Gordon's user document on Pronto Hex IR Format in the Classic Pronto Files Section. Barry has done a very nice job explaining the format.
And, a read through this will also help you better follow Buzz's earlier suggestion about repeats.
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