Editting a datatable

I've got a datatable and I want to loop through and edit the value of a single cell in each row. How do I go about doing that? I've tried the following, but it hasn't worked:

Code:

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Dim i, j, iSum As Integer
For i = 0 To dt.Rows.Count - 1
    dt.Rows(i).BeginEdit()
    If i = 0 Then
        dt.Rows(i).Item(6) = CInt(dt.Rows(i).Item(5)).ToString
    Else
        For j = 0 To i
            iSum += CInt(dt.Rows(i).Item(5))
        Next
        dt.Rows(i).Item(6) = iSum.ToString
    End If
    dt.Rows(i).EndEdit()
    dt.Rows(i).AcceptChanges()
Next
dt.AcceptChanges()

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Any thoughts?

Just glancing over the code, I don't see anything wrong. You say it doesn't work. What happens or doesn't happen that makes you say that?
Is the datatype for item(6) String?