Change pointers with custom message type

Hi Gurus,

              I have a requirement on Idoc, i.e whenever user change the particular fields data in the transaction (PA30) and then he click on save, automatically the changes should trigger the idoc.

To achieving this functionality, I have do the following steps:

WE31  :   Segment creation    (With the Particular fields of PA30)

WE30  :   Basic Idoc creation  (With above segment)

WE81  :   Logical Message Type creation

WE82  :   Assign the Idoc to Message type

BD50   :   Activate the Message type (change pointer)

BD64   :   Distribution Model Created with the above Message type

And finally i have done the configuration things to trigger the idoc.

After that i executed the transaction PA30, and make some changes on particular fields,finally i executed the transaction BD21 with my own message type. The result will be like this ' Data not found', it won't trigger the idoc.

Please guide me to trigger the Idoc.

Thanks in Advance

Regards,

SR Krishna.