I have a similar question, but related to simple text formatting. For example, the Dynamic text item for a map center, when given the unit value 'mgrs' and round of 0 returns '60HXD' (i.e. the UTM zone and grid square) as its smallest value. I want to take that value and just display, for example, the first 3 characters (i.e. 60H) or the last 2 (i.e. XD).
It doesn't appear that you can assign the value of a dynamic string and then modify it?