The "@ExpandNameList" is an undocumented formula which can be used in resolving the groups.
Below is a simple version of the code to resolve the Group in a field:
Place following code in Input translation event:
On change event Place the following code to refresh the document
_doClick('$Refresh', this, '_self', '#_Refresh<Field Name>')
Note: There should not be space between #_Refresh and the Field Name. This code will also evaluate the names/short names (Should be unique in your Domino directory(or address book)) to their hierarchal name/email address.
The draw back of using this method is "if resolved group name contains more than 64K then an error page will be displayed". This page could be avoided using the error handler in formula language.