Perhaps it would be easier to understand, if I explained the process.

1. The Dialogue Box is displayed when the letter is opened, the User fills it in and it closes once the OK button is clicked.

2. All of the required fields in the letter are populated with the information entered by the User on the first page of the letter.

3. Subsequently, other code is run by the User to insert a second page into the letter and instead of the required field in the Header being populated from the original Dialogue Box, the Run-time error is displayed.

I hope this makes more sense.

Regards
Useful