After deeper internet search it seems that in 2007 that was impossible with pure VBA code.
"When the macro language changed from WordBasic to VBA, the developpers
messed up and defined the position as a Long (integer), although half points
are allowed."
And I think it is the same now in 2017.
Luckily, it can be bypassed with pieces of WordBasic code that can be inserted in the VBA macro code:
Code:
With WordBasic
.EditFindClearFormatting
.EditReplaceClearFormatting
.EditFindClearFormatting
.EditFindFont Position:="4.5"
.EditReplaceFont Superscript:=True
.EditReplace Format:=1, Wrap:=1, ReplaceAll:=True
End With