Oh I know what the problem is the coma's try this if it still gives you an error write a subroutine.
iff((Mid(homephone,4,1="

"

),(Mid(homephone,2,2) & Mid(homephone,6,10)), (Mid(homephone,2,4) & Mid(homephone,7,10)))
the subroutine will go something like this
sub updateit()
Dim dbs As Database
Dim rstSet As DAO.Recordset
Dim tmpPhone as string
set dbs=currentdb
set rstSet=dbs.OpenRecordset("tablename"
rstSet.MoveFirst
do until rstSet.EOF
rstSet.Edit
tmpPhone=rstSet![phonefield]
if Mid(tmpPhone,4,1="

"

then
rstSet![homephone]=Mid(tmpPhone,2,2) & Mid(tmpPhone,6,10)
else
rstSet![homephone]=Mid(tmpPhone,2,4) & Mid(tmpPhone,7,10)
rstSet.Update
rstSet.MoveNext
loop
end sub
This should work