Reports :: Report Of Pivot With Dates

I have a table with columns

position, DateTime, value
(datetime being a text field by the way, not my fault :-))

I wrote a simple pivot query

TRANSFORM Avg(value) AS AvgOfvalue
SELECT Position
FROM table
WHERE (dateTIME)>format(Date()-2,"DD-MMM-YY")
GROUP BY position
PIVOT dateTIME;

The idea was that I could report each last 2 days with this query.The pivot query works OK.Creating a report based on this query, the control source of the fields is linked to columns like "12-JUN-15 07:00" which will not be available after some days.Isn't it possible to create a pivot report on a pivot query based on dates?