sum of row value date wise

Question

create table Table1
(
TB1_ID varchar(100),
TB1_DT varchar(100),
TB1_PRC varchar(100),
TB1_US varchar(100)
)
 
select * from Table1

and

my table is:

TB1_ID  TB1_DT        TB1_PRC   TB1_US
 
1	2/8/2013	100	60
2	5/8/2013	1000	600
3	7/8/2013	11000	6100
4	8/8/2013	12000	6200
5	9/8/2013	13000	6300

 
i want to get average(for many values) of TB1_PRC from TB1_DT 5/8/2013 to 10/8/2013.
but how.........