Dynamic Values in Oracle FND messages

Hi,

I need to undertsnad how to use dynamic values in the fnd messages in R12. For eg: suppose we have make an email subject using fnd_messgaes, this email subject should include the invoice number on the basis of the invoice number parameter used while running the program that uses the fnd_message.

In layman terms, the invoice number should change in the subject line on the basis of the invoice number in the email or from the invoice number from the email attachment.

Please suggest if any Oracle note is available to demonstrate the same.

thanks in advance.