Dim dic As new Dictionary(of String,Integer)
For Each dr1 As DataRow In DataTables("生产计划").DataRows
    For Each dr2 As DataRow In DataTables("零件用量").Select("[产品] = \'" & dr1("产品") & "\'")
        Dim nm As String = dr2("零件")
        Dim vl As Integer = dr1("生产数量") * dr2("用量")
        If dic.ContainsKey(nm) = False
            dic.Add(nm,vl)
        Else
            dic(nm) = dic(nm)+ vl
        End If
    Next
Next
For Each key As String In dic.keys
    Dim dr As DataRow = DataTables("零件需求").AddNew()
    dr("零件") = key
    dr("需求数量") = dic(key)
Next

  根据这个代码  如果在生产计划再添加新的产品和数量   我怎么执行这个代码?

  前提是不能清除已经计算过的零件了!!!!!!!