minus two values

[maqza]

Hi,
I have one table like
code price date
10A 1500 10/07/06
10B 1600 10/07/06

11A 1300 10/07/06
11B 1500 10/07/06

just i want to to display in query

code price date differprice
10A 1500 10/07/06 100 (eg 10A price -10B price)
10B 1600 10/07/06 100

11A 1300 10/07/06 200
11B 1500 10/07/06 200

please help me
Regards
Maqza