Can anybody help me for Average Purchase Rate of Item During Sales Entry

Hello everyone,
I am a new user, first of all i want to say that u are doing a great job, it is very helpful to every businessman using tally. Such a great work u doing.

Further i want to say that i need a tdl file to Display Average Purchase Rate of Item During Sales Entry , if anybody can help me, pls send me the tdl for this.

Thanks and regards,

Vivek Nagdeo.