Availability check against transference

Gurus,

My cumulative ATP is not considering transference so I have been problem to confirm order. Although my check instruction is set up with category BH, AG,BI and BF.

Scenary:

Product: ABC

Plant: Plant X / Plant Y

Transference: From: Planx --ABC-> To Planty (There is a Transportation Lane created)

Inicial Stock: Stk (Plant X) = 3000 Plant Y(100)

I executed MRP in plant Y then in plant X. When I started analize the result, I noticed that demand from plant Y creates a requirement to plant X. The material ABC is an external procurement in plant Y so a purchase requirement (PurRqs) was created instead of PReqRel in Plant X

My MRP scenery is described bellow:

product: ABC/Plant X

STK 3000

SO 2000 (not confirmed)

PReqRel -2000

The cumulative ATP doesn´t consider the PReqRel to promise data. So, My order would be confirmed completly if execute ATP by BOP or VA.

My expected result is 1000 of confirmed order instead 2000.

How it is appearing in production view:

/sapapo/rrp3

Field: ATP

Av. req. date 13.12.2011

Av. Reqments time 00:00:00

Category PurRqs

Rec. Reqmsnt Element 500000001006

Rec. Reqmts qty 10.000

Confirmed/ Request 10.000

Cumulative ATP (The same as before)

ATP quantity/ Unit -

-

I would be glad with your help.