如果值已经存在，VBA 宏不会将单元格复制到另一个工作表

Question

I have a list of about 5000 contacts with their information organized by the work they perform. Some are listed multiple times if they perform several types of work. I use the list to send notifications to the contacts if they've been selected in accordance with the work they perform.

I use the Email Merge function to send individual emails and so I wrote a macro to copy the contact's email over to another worksheet if they've been selected.

Sub CopySelectedMasterToMerge()

Dim RangeToConsider2 As Range
Dim strAddresses2 As String
Dim shtSrc As Worksheet, shtDest As Worksheet

Set shtSrc = Sheets("MASTER")       'source sheet
Set shtDest = Sheets("Email Merge")  'destination sheet
destRow = 2                         'start copying to this row
Set RangeToConsider2 = Range("K4:K7000")

For Each Cell In RangeToConsider2
If Cell.Value = "a" Then
    If Cell.Offset(0, 1) <> "ZZZZZZZZZ" Then
        Cell.Offset(0, 6).Cells.Copy shtDest.Cells(destRow, 1)
    destRow = destRow + 1
    End If
End If
Next Cell
Worksheets("Email Merge").Activate
End Sub

This, along with the Email Merge, work really well except the contacts with multiple listings are receiving additional copies of the same email.

How can I prevent an email being copied over again if it already exists on the other Worksheet?

Update - using @BigBen's suggestion, I got the WorksheetFunction.CountIf to work.

For Each Cell In RangeToConsider2

    If Cell.Value = "a" Then
        EmailAddress = Cell.Offset(0, 6)
        If Cell.Offset(0, 1) <> "ZZZZZZZZZ" Then
            CountCheck = WorksheetFunction.CountIf(SearchArea, EmailAddress)
            If CountCheck < 1 Then
                 Cell.Offset(0, 6).Cells.Copy shtDest.Cells(destRow, 1)
            destRow = destRow + 1
            End If
        End If
    End If
Next Cell

Answer 1

If I understand you correctly you are copying email addresses from one sheet to another based on criteria and you want the resulting list to be unique?

You could use an intermediate structure like a Collection or a Dictionary to test for uniqueness.

A Dictionary is a key-value structure where the keys must be unique. The value can be the same as the key. I prefer to use a Dictionary because it has a built in function to test for the existence of a key. If you used a Collection you would have to write your own:)

Basically as you run through the list of emails you test for their existence in the Dictionary and only add new entries. You then use the Dictionary contents to decide who to mail to - you don't even need to copy them to a new sheet. Of course you still can if you need them for some other purpose.

Here is an excellent tutorial on what they are and how to use them.