Excel VBA Question – How can I optimize this code?

Function RegExpFind(FindIn, FindWhat As String, Optional Index As Integer, _
        Optional IgnoreCase As Boolean = True)
    Dim i As Long

    Dim RE As RegExp, allMatches As MatchCollection, aMatch As Match
    Set RE = New RegExp

    RE.pattern = FindWhat
    RE.IgnoreCase = True
    RE.Global = True
    Set allMatches = RE.Execute(FindIn)

    ReDim rslt(0 To allMatches.Count - 1)

    For i = 0 To allMatches.Count - 1
        rslt(i) = allMatches(i).Value
    Next i

    RegExpFind = rslt
End Function