You can of course create your own functions, but for it to work correctly with the add-in you need to follow the format set out on the web page - in particular the items commented below. Different Word versions use style sets differently, but if the recorder gives the style set name as you have it it will probably work in your version.
Code:
Function changeStyle(oDoc As Document) As Boolean
On Error GoTo Err_Handler
'Do Something with oDoc here. e.g.,"
oDoc.ApplyQuickStyleSet2 ("Template")
changeStyle = True 'the name of the function = true
lbl_Exit:
Exit Function
Err_Handler:
changeStyle = False 'the name of the function = false
Err.Clear
GoTo lbl_Exit
End Function
You can also apply individual styles to the header footer ranges (or parts of the ranges) in the original macro, but the styles should be stored in the autotext entries and so this should be unnecessary. The problem will be that you have different styles with the same names in the target documents, so you could copy the styles used in your autotexts from the normal template to the document, which can be done in the same macro or perhaps better still use unique style names for your header and footer in the autotext so there is no conflict.