Schleife falsch

Sub Zaehlen()
Dim rng As Range
Dim a As String
Dim b As String
Dim cell As Range
Dim LR As Long
With Sheets("SaP500")
LR = .Range("O" & Rows.Count).End(xlUp).Row
For Each cell In Sheets("SaP500").Range("L1:L900" & LR)
If cell.Value  "" Then
If rng Is Nothing Then
Set rng = cell
Else
Set rng = Union(rng, cell)
End If
End If
Next cell
a = Cells(ActiveCell.Row, 1).Value
b = Cells(ActiveCell.Row + 1, 1).Value
MsgBox "Entered value is " & a & b
End With
End Sub