Membuat Auto Number Rolling..

Private Sub frmTransPenjualanBaru_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    RandomCharAndNum()

End Sub

Private Sub RandomCharAndNum()

    Dim tahun = Format(CDate(DateAndTime.Now), "yMMddhhss")

    TextBox1.Text = RandomString(4, _chars) & tahun & RandomString(2, _nums)

End Sub

Private Const _chars As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

Private Const _nums As String = "0123456789"

Private Shared ReadOnly _randLock = New Object()

Private Shared ReadOnly _rnd = New Random()

Private Shared Function RandomString(ByVal size As Integer, ByVal chars As String) As String

    Dim arr = New Char(size - 1) {}

    For i As Integer = 0 To size - 1

        SyncLock _randLock

            arr(i) = chars(_rnd.Next(chars.Length))

        End SyncLock

    Next

    Return New String(arr)

End Function