Try:
{QUOTE{IF{MERGESEQ}= 1 "{SET Key1 ""}{SET Key2 ""}"}"{IF{MERGEFIELD ED}<> {REF Key1} "{IF{MERGESEQ}> 1 {QUOTE 12}}{MERGEFIELD ED}{SET Key1 {MERGEFIELD ED}}¶
"}{IF{MERGEFIELD NUM}<> {REF Key2} "{SET Key2 {MERGEFIELD NUM}}¶
{MERGEFIELD NUM}¶
"}{MERGEFIELD LAST} {MERGEFIELD FIRST}¶
"}
Note: You'll need to replace the ¶ symbols with real paragraph breaks or line breaks. You also need all of the spaces indicated - the field 'code' in your post is missing numerous critical spaces.
For a macro to convert the above to a working field code, see:
http://www.gmayor.com/export_field.htm#TextToField