Mini Control de Stock vb2008 - restas y sumas

[javiercapi]

Muy currado tu post

copia y pega en tu codigo y mira a ver si es esto lo que quieres, es lo que me parecio entender

Código:

    Dim cn As OleDbConnection
    Dim cmd As OleDbCommand
    Dim lector As OleDbDataReader
    Dim ruta As String = "C:\foro\mibase.mdb"


    Private Sub Stock_Actual()

        cn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; Data Source=" & ruta & "")
        cmd = New OleDbCommand("select cantidad from mitabla", cn)

        cn.Open()
        lector = cmd.ExecuteReader
        lector.Read()

        If lector.HasRows Then
            txttotal.Text = lector.Item(0)
        End If

        lector.Close()
        cn.Close()

    End Sub

    Private Sub btnvender_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnvender.Click

        If txttotal.Text >= 10 Then

            cn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; Data Source=" & ruta & "")
            cmd = New OleDbCommand("UPDATE mitabla SET mitabla.cantidad = " & txttotal.Text & "-" & txtvender.Text & "", cn)

            cn.Open()
            cmd.ExecuteNonQuery()
            MsgBox("Venta ok")
            cn.Close()

            Stock_Actual()

        Else
            MsgBox("no se puede vender más")
        End If
        

    End Sub

    Private Sub btncomprar_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btncomprar.Click

        cn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; Data Source=" & ruta & "")
        cmd = New OleDbCommand("UPDATE mitabla SET mitabla.cantidad = " & txttotal.Text & "+" & txtcomprar.Text & "", cn)

        cn.Open()
        cmd.ExecuteNonQuery()
        MsgBox("Compra ok")
        cn.Close()

        Stock_Actual()


    End Sub

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        Stock_Actual()

    End Sub