Where can I find the Billing Doc. Header Text SO10 text name?

I have to write some logic in the billing document header text “country of origin”.

1. VF02-- GOTO-- HEADER---HEADER TEXT----- COUNTRY OF ORIGIN.

When a billing document is created it automatically creating the header text with the following details:

Name :                       Billing doc number

Language : EN

Text ID:        ZD17

Text object : VBBK.

I need to find the SO10 text name from which the above dynamic text is generating, so that I can change the code in the original text..

I searched in the SCN and found the Tcode VOTXN.

I went to this tcode and selected the Billing Doc. Header Radio button.

And I found the Access sequence number corresponding ID(ZD17-country of origin)

When I gone through the sequence number I found one SO10 text name, but that is not the right SO10 name because the contents are totally deferrent.

is there any way to find the SO10 text name, or did I went to any wrong path...

please help me..

Regards,

Ramesh