PL/SQL :: Parsing Date With MM.YYYY And Between

I got a table with a Date in it. Lets called it Testdate and an item called start month and end month.

The Item (varchar2) looks like

MM.YYYY f.e. 03.2012 and is a

I want to see all data between start and endmonth.

First I tried to convert the date from my orignial table:

SELECT distinct TO_CHAR(TESTDATE, 'MM'||'.'||'YYYY')
FROM mv_auswertung;This works:

TO_CHAR(TESTDATE,'MM'||'.'||'YYYY')
02.2012
12.2012
01.2012

But now I am trying to get all data between start and enddate:

Select *
from mv_auswertung
where
TO_CHAR(TESTDATE, 'MM'||'.'||'YYYY') between
to_CHAR(:P7_startmonth) and to_char(:P7_endmonth)