This will work if you only have two Value to work with but I see more than
two in some cases of your example.  

Use two queries. I named the first one Query58 from Table20 so you can
change accordingly.

SELECT [RecID] & [SubID] AS Identification, First(Table20.Value) AS
FirstOfValue, Last(Table20.Value) AS LastOfValue
FROM Table20
GROUP BY [RecID] & [SubID];

SELECT Query58.Identification,
IIf([FirstOfValue]=[LastOfValue],[FirstOfValue],[FirstOfValue] & ", " &
[LastOfValue]) AS Type
FROM Query58;

Hi,

In two steps. First, create a temp table that will get the two fields, and
unique ID (drop the table if it already exists, before)

SELECT DISTINCT id, iif(false, "", null) As concat INTO temp FROM mytable

Finally, create the various concatenations with a SET over a standard INNER
join:

UPDATE temp INNER JOIN myTable ON temp.id=mytable.id
SET temp.concat = ( temp.concat + ",  " )  & mytable.value

The result is now in the table temp.

Hoping it may help,
Vanderghast, Access MVP