Enter Data to Different Accounts and save your content

I need you to help me with something, I am making a system and in one of the forms I have to enter notes to the students according to the account number, what I need is that when entering a different account the data is saved only for That account I am working on Sql Server and in Visual Basic. My save code is this:

 Dim cmd As New SqlCommand()

 cmd.Connection = conexion

 Dim Agregar As String = "INSERT INTO Clases(n_Cuenta, Nombre, codClase, Nota, Cursadas, Promedio)"

Agregar += "VALUES('" & nCuenta.Text & "','" & Nombre.Text & "','" & codClase.Text & "'," & Nota.Text & "," & Cursadas.Text & ",'" & Double.Parse(Nota.Text) & "')"

cmd.CommandText = Agregar

cmd.ExecuteNonQuery()

MsgBox("Guardado Con Exito")