I have worked this one out.
You have to pass a range then autofill from the range.

ox.Cells(435,4).Value = '=IF(ISNA(MATCH($A$69,E71:E435,0))=TRUE,0,MATCH($A$69,E71:E435,0))'
WITH ox.activeworkbook.worksheets(1)
.Range("D435").AutoFill(.Range("D435:AY435"),0) && 0 = xlFillDefault
ENDWITH

Hopefully this might be of some use to others.

Martin