帮我看看这个购物车添加不进去

用2016 ACCESS购物老是添加不进去.提示“请选择当前客户”我已经添加当前客户怎么还不行，请帮忙看看怎么修改。这不是我写了，我也是学习中，请老师指点一下。

Private Sub 放入_Click()
Dim ssql As String
  
If Nz(MYnum, 0) = 0 Or Nz(Me.销售ID.Value, 0) = 0 Then
    MsgBox "请选择当前客户！"
Else
    ssql = "INSERT INTO 销售明细 ( 销售ID, 商品ID,数量,实际售价,金额 ) VALUES ("
    ssql = ssql & Me.销售ID.Value & "," & MYnum & "," & 1 & ","
    ssql = ssql & DLookup("标准售价", "商品表", "商品ID=" & MYnum) & ","
    ssql = ssql & DLookup("标准售价", "商品表", "商品ID=" & MYnum) & ")"
    DoCmd.SetWarnings False
    DoCmd.RunSQL ssql
End If
End Sub