Linking/Unlinking Previous

The LinkToPrevious property applies to each type of header and each type of footer separately.
Setting this to True automatically inserts text into all headers (and footers)
Setting this to False does not automatically remove the text.

objHeaderFooter.LinkToPrevious = True | False 

The following will unlink the current header from the previous header

iNoOfSections = ActiveDocument.Sections.Count 
With Application.ActiveDocument.Sections(iNoOfSections).Headers(wdHeaderFooterIndex.wdHeaderFooterPrimary) 
   .LinkToPrevious = False 
   .Range.Delete  ''this line deletes everything from the header to make sure it is blank  
End With 

The following will unlink the current footer from the previous footer

iNoOfSections = ActiveDocument.Sections.Count 
With Application.ActiveDocument.Sections(iNoOfSections).Footers(wdHeaderFooterIndex.wdHeaderFooterPrimary) 
   .LinkToPrevious = False 
   .Range.Delete  ''this line deletes everything from the header to make sure it is blank  
End With