[CONNECT C++] Formatting using ECN::IECInstance

I have a text field populated with the API's default formatting.  It's an area measurement and looks something like Area: 134.3201 Sq. m, where Area: is user-supplied text and 134.3201 Sq. m is a text field derived from an element's EnclosedArea property.

I would like to reformat that area: for example, lose some decimal precision and use engineering notation: Area: 134.32 m².  I've found the following in MicroStationAPI help but with few notes about their use...

WString FormatValue  ( ECN::ECValueCR  v,  
  DgnECInstanceCR  source,  
  WCharCP  accessString  
 )  const; 

ECN::IECInstanceCP  GetFormatter () const;  

Returns the options describing how to format the field's display value, or nullptr if no special formatting options are defined.

However, the IECInstance documentation provides no clue about formatting.  How do I define special formatting options?