Check if String is exist in dictionary

Please help.

I'm new to dictionary.

Something wrong.

trying to check if the string already in the dictionary.

Dim dic As Object

Set dic = CreateObject("system.collections.arraylist")
Set twb = ThisWorkbook
Set tws = twb.Sheets("Array1")
Set FX = twb.Sheets("Array2")
Dim Key
Dim item
    
    For i = 1 To Application.WorksheetFunction.CountA(tws.Columns(1))
      Key = tws.Cells(i, 1) & tws.Cells(i, 2) & tws.Cells(i, 5) & tws.Cells(i, 6) & tws.Cells(i, 13)
      dic.Add Key
    Next
    
    For Z = 1 To Application.WorksheetFunction.CountA(FX.Columns(1))
    item = FX.Cells(Z, 1) & FX.Cells(Z, 2) & FX.Cells(Z, 4) & FX.Cells(Z, 5) & FX.Cells(Z, 6)
    If dic.Exists(item) Then
        FX.Cells(Z, 1).Style = "Bad"
        FX.Cells(Z, 2).Style = "Bad"
        FX.Cells(Z, 4).Style = "Bad"
        FX.Cells(Z, 5).Style = "Bad"
        FX.Cells(Z, 6).Style = "Bad"
        FX.Cells(Z, 7).Value = "Duplicate"
        FX.Cells(Z, 7).Style = "Bad"
    End If
Next

Set dic = Nothing

Big Thanks,