dilerim işinize yarar
sonuç doğru gibi geldi ama siz yine de test edin)

Dim txtGec, txtGec2 As String

Dim BytSnr As Byte



txtGec = Me.urun_tanim

Me.tanim1 = ""

Me.tanim2 = ""

Me.tanim3 = ""



For x = 1 To 3

if x=3 then 

      Controls("tanim" & x).Value = left(txtGec,80)

      exit for

end if

txtGec2 = Left(txtGec, 81)

If Len(txtGec2) < 81 Then

    Controls("tanim" & x).Value = txtGec2

    Exit For

End If

BytSnr = InStrRev(txtGec2, "/")

Controls("tanim" & x).Value = Left(txtGec, BytSnr - 1)

txtGec = Mid(txtGec, BytSnr + 1)

Next x

yada

Dim x, y As Byte

Dim MetBol() As String

Dim txtGec, txtMetBol, txtMetBol2 As String

Me.tanim1 = ""

Me.tanim2 = ""

Me.tanim3 = ""

txtMetBol2 = Me.urun_tanim



For y = 1 To 3

    If Len(txtMetBol2) < 80 Then

        Controls("tanim" & y).Value = txtMetBol2

        Exit For

    End If

MetBol = Split(txtMetBol2, "/")

txtMetBol = MetBol(0)

   

   For x = 1 To UBound(MetBol)

        txtGec = txtMetBol

        txtMetBol = txtMetBol & "/" & MetBol(x)

        Controls("tanim" & y).Value = txtMetBol

        If Len(txtMetBol) > 80 Then

            Controls("tanim" & y).Value = txtGec

            txtMetBol2 = Mid(txtMetBol2, Len(txtGec) + 2)

            Exit For

        End If

    Next x

Next y