Public Class Form1
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        Dim text As String = "Dies ist mein superlanger Text, den ich auf" & _
        "mehrere Zeilen aufteilen will !!!"
        Me.TextBox1.Text = SplitString(text, 20)
    End Sub
 
    Private Function SplitString(ByVal text As String, ByVal length As Integer)
        Dim temp() As String = text.Split(" ")
        Dim ret As String = ""
        Dim currentlength As Integer = 0
        For i As Integer = 0 To temp.Length - 1
            If currentlength < length Then
                currentlength += (temp(i) & " ").Length
                ret &= temp(i) & " "
            Else
                ret &= temp(i) & vbCrLf
                currentlength = 0
            End If
        Next
        Return ret
    End Function
End Class