Compairing 2 sheets selected from a userform

[jimayers]

Hello - I have a code to populate a userform of all the sheets:

Private Sub UserForm_Activate()
Application.ScreenUpdating = False
Dim r, NumShts As Long
Dim i As Integer
NumShts = ThisWorkbook.Worksheets.count
With UserForm2
    i = 0
    .ListBox2.Clear 'clear all existing list box items
        'populating listbox2 with sheet names
        For r = 1 To NumShts
            .ListBox2.AddItem
            .ListBox2.List(i, 0) = ThisWorkbook.Worksheets(r).NAME
            i = i + 1
        Next r
End With
Application.ScreenUpdating = True
End Sub

I want to use 2 of the chosen sheets from the userform2 and compare data in column 2. When there is duplicate records I would like to highlight a certain cell. I am having trouble, and am wondering if I need to put the column B data in an array to compare first.

Thanks for any help - Jim A