UPDATE QUERY -SQL SERVER 2005

[Mahey]

Hi,

I want to update the table like the following manner.

Field "Item_Description" is having the data's

ASMITEMS for department
BSDBILL -systems
RVF..........
ASM..........
TYP........
BSD..............
ASM..................

THANKS

But I want to update like the "itm_code" by following
[only 1st 3 letters+Counts)

ASM1
BSD1
RVF1
ASM2
TYP1
BSD2
ASM3

like wise ...means when the value is found again, need to increase the counter

update itm_code set itm_code=substring(Itm_description,1,3)+.............from item_master....????