Funktion funktioniert nicht mit Datum

Public Function fcnSumIfMySheets(crit As Range, strt As Long, fnsh As long) As Double
On Error Resume Next
Dim dCondSum As Double
Dim lBgn As Long
Dim lEnd As Long
lCondSum = 0
lBgn = strt
lEnd = fnsh
For i = lBgn To lEnd    'e.g. from Sheetx to Sheety
If Not Worksheets(i) Is Nothing Then
dCondSum = dCondSum + Application.SumIf(Worksheets(i).Range("A:A"), crit.Value,  _
Worksheets(i).Range("C:C"))
Else
fcnSumIfMySheets = dCondSum
Exit Function
End If
Next
fcnSumIfMySheets = dCondSum
End Function