Bom dia.
Considerando seus dados na coluna "A" (Pode ser outra, neste caso devera mudar a macro)), a partir de A2.....An.
Sub MaiorIntervalo()
Dim c As Range, mi As Long, mf As Long, k As Long
Application.ScreenUpdating = False
ActiveSheet.AutoFilterMode = False
If [a1] = "" Then [a1] = "X"
ActiveSheet.[a1].AutoFilter 1, 1
mi = 1
For Each c In Range("a2:a" & Cells(Rows.Count, 3).End(3).Row).SpecialCells(xlVisible)
If c.Row - mi > k Then k = c.Row - mi - 1
mi = c.Row
Next c
ActiveSheet.AutoFilterMode = False
MsgBox "MAIOR INTERVALO = " & k
End Sub
Veja se funciona.
Até
Foxtri