How to enable textbox during attachment step in New Part Request

hello,

During creation of New Part Request, in the attachment wizard step i want to one more column in the table as ATTACHMENT DESCRIPTION FOR SUPPLIER with text box.

I have customize the jsp file for attachment step and added one more option as ATTACHMENT DESCRIPTION FOR SUPPLIER but the text box would not be enabled as same happened for Attachment Description column.

Please let me know, which is the exact file where i can enable the text box for custom column ATTACHMENT DESCRIPTION FOR SUPPLIER in Attachment wizard step for New Part Request.Below is the screen shot for same.

Thanks in advance.

Regards,

Arpit Shah