Help with RANKX

[masplin]

Is it possible to use RANKX to get either of the 2 results below?

<tbody>
</tbody>

[TABLE="width: 449"]
<tbody>[TR]
[TD]Match Ref[/TD]
[TD]Inv Last Mod Date[/TD]
[TD]RankX[/TD]
[TD]RankX[/TD]
[TD]Formula[/TD]
[/TR]
[TR]
[TD="align: right"]16982[/TD]
[TD="align: right"]19/06/2013 12:32[/TD]
[TD="align: right"]1[/TD]
[TD="align: right"]1[/TD]
[TD="align: right"]1[/TD]
[/TR]
[TR]
[TD="align: right"]34330[/TD]
[TD="align: right"]14/06/2013 14:51[/TD]
[TD="align: right"]2[/TD]
[TD="align: right"]2[/TD]
[TD="align: right"]2[/TD]
[/TR]
[TR]
[TD="align: right"]16982[/TD]
[TD="align: right"]13/12/2012 13:23[/TD]
[TD="align: right"]1[/TD]
[TD][/TD]
[TD="align: right"]2[/TD]
[/TR]
[TR]
[TD="align: right"]16982[/TD]
[TD="align: right"]18/06/2012 13:37[/TD]
[TD="align: right"]1[/TD]
[TD][/TD]
[TD="align: right"]2[/TD]
[/TR]
[TR]
[TD="align: right"]16982[/TD]
[TD="align: right"]18/06/2012 13:36[/TD]
[TD="align: right"]1[/TD]
[TD][/TD]
[TD="align: right"]2[/TD]
[/TR]
[TR]
[TD="align: right"]16982[/TD]
[TD="align: right"]21/12/2011 14:19[/TD]
[TD="align: right"]1[/TD]
[TD][/TD]
[TD="align: right"]2[/TD]
[/TR]
[TR]
[TD="align: right"]16982[/TD]
[TD="align: right"]20/10/2011 16:54[/TD]
[TD="align: right"]1[/TD]
[TD][/TD]
[TD="align: right"]2[/TD]
[/TR]
[TR]
[TD="align: right"]34330[/TD]
[TD="align: right"]21/06/2011 11:38[/TD]
[TD="align: right"]2[/TD]
[TD][/TD]
[TD="align: right"]7[/TD]
[/TR]
</tbody>[/TABLE]
I tried (where all the above are same Reg Num)

=      RANKX(
               FILTER(MatchInput,
                              [Reg Num]=EARLIER([Reg Num])  && [Match Ref]<>EARLIER([Match REF])
                             ),
               [Inv Last Mod Date]
              ,,0,dense
              )

but gives me the last column which makes no sense to me?

Thanks Mike