Option Explicit
Sub TEST()
Dim Brr, Y, i&, xR As Range
Set Y = CreateObject("Scripting.Dictionary")
Set xR = Range([C1], Cells(Rows.Count, "A").End(xlUp)): Brr = xR
For i = 2 To UBound(Brr): Y(Brr(i, 1)) = "": Next
MsgBox "共有 " & Y.Count & " 個箱號"
Set Y = Nothing: Set xR = Nothing: Erase Brr
End Sub