You can address any part of the document from the userform, by setting a range to the area you wish to work in. If you put a bookmark in the header e.g. bmHeader then you can write text to that bookmark using the FillBM function you will find at
http://www.gmayor.com/useful_vba_functions.htm then call it from your macro as follows
Code:
FillBM "bmHeader", "Some Text"