Excel formulas based on inventory management

Actually I am stuck in a typical situation here, and I really need your help:

So, I am trying to create a Inventory database here as follows:

1) STOCK IN SHEET (SHEET -1) (here I want to enter my data with the below given format):

column--> A // B // C
1 PRODUCT ID // ITEM // STOCK IN
2 A12 // T-SHIRT // 10
3 A13 // JEANS // 5
4 A14 // SHIRT // 10
5 A15 // TIE // 5
6 A12 // T-SHIRT // 8
7 A12 // T-SHIRT // 10
8 A14 // SHIRT // 12
9 A15 // TIE // 10



2) ITEM DESCRIPTION (SHEET 2): (HERE I WANT THOSE DATA AUTOMATICALLY GETS UPDATED (FROM SHEET -1) WITHOUT ANY DUPLICATE ENTRY WITH UNIQUIE PRODUCT ID)

column--> A // B // C
1 PRODUCT ID // ITEM // ITEM DESCRIPTION
2 A12 // T-SHIRT // HALF SLEAVE, COTTON, BLUE
3 A13 // JEANS // DENIM, BLACK
4 A14 // SHIRT // FULL SLEAVE, COTTON, WHITE
5 A15 // TIE // POLYESTER, SOLID SILVER


3)CURRENT INVENTORY (SHEET 3): (LIKE SHEET 2, IT WILL ALSO AUTOMATICALLY GETS UPDATED FROM STOCK IN (SHEET-1), BUT IT WILL ALSO KEEP THE TRACK OF TOTAL STOCK CALCULATION [i.e QUANTITY STOCK IN (SHEET 1) AND QUANTITY STOCK OUT/SOLD (SHEET -4)] SIMULTANEOUSLY:

column--> A // B // C
1 PRODUCT_ID // ITEM // INVENTORY
2 A12 // T-SHIRT // 22 [ STOCK IN : 10+8+10 = 28 ; STOCK SOLD: 2+3 = 5 ; CURRENT INVENTORY =22 (28-5)]
3 A13 // JEANS // 4
4 A14 // SHIRT // 22
5 A15 // TIE // 10


4)STOCK SOLD LIST (SHEET -4):

column--> A // B // C // D
1 BILL_NO // PRODUCT_ID // ITEM // QUANTITY
2 111 // A12 // T-SHIRT // 2
3 112 // A13 // JEANS // 1
4 113 // A12 // T-SHIRT // 3
5 114 // A15 // TIE // 5


Please help me with this.