Customizing close opportunity dialogue box in crm 4.0

I need to add a new field to the close opportuni开发者_JS百科ty dialog box.

Is there any way to do this?

This Form is not covered by the SDK and therefore not customizable. You could try to edit the .aspx-file, which is totally unsupported, but you are not able to change the built-in process of this dialog.

See the list of Unsupported changes