主题：产品与模具的关系

物料字典_DataColChanged

Select Case e.DataCol.Name
    Case "模具型号","物料编号"
        Dim dr As DataRow = DataTables("模具清单").Find("模具型号='" & e.DataRow("模具型号") & "'")
        If dr Is Nothing Then
            dr = DataTables("模具清单").AddNew
            dr("模具型号") = e.DataRow("模具型号")
        End If
        dr("所应用的产品") = e.DataTable.GetComboListString("物料编号","模具型号='" & e.DataRow("模具型号") & "'").Replace("|",",")
        If e.DataCol.Name = "模具型号" AndAlso e.OldValue > "" Then
            dr = DataTables("模具清单").Find("模具型号='" & e.OldValue  & "'")
            If dr IsNot Nothing Then
                dr("所应用的产品") = e.DataTable.GetComboListString("物料编号","模具型号='" & e.OldValue & "'").Replace("|",",")
            End If
           
        End If
End Select

物料字典_DataRowDeleting

Dim dr As DataRow = DataTables("模具清单").Find("模具型号='" & e.DataRow("模具型号") & "'")
If dr IsNot Nothing Then
    dr("所应用的产品") = e.DataTable.GetComboListString("物料编号","模具型号='" & e.DataRow("模具型号") & "' and [_Identify] <>" & e.DataRow("_Identify")).Replace("|",",")
End If

没看懂你需要做什么效果，先试试

Select Case e.DataCol.Name
    Case "模具型号"
        If e.DataRow("模具型号") <> "不适用"
            Dim drs = DataTables("模具清单").Select("模具型号='" & e.DataRow("模具型号") & "'")
            Dim str = e.DataTable.GetComboListString("物料编号","模具型号='" & e.DataRow("模具型号") & "'").Replace("|",",")
            For Each dr As DataRow In drs
                dr("所应用的产品") = str
            Next
        End If       
End Select

If e.DataCol.Name = "模具型号" AndAlso e.OldValue > "" AndAlso e.newvalue <> "不适用" Then
   
    Dim drs1 = DataTables("模具清单").Select("模具型号='" & e.DataRow("模具型号") & "'")
   
    Dim drs2 = DataTables("模具清单").Select("模具型号='" & e.OldValue  & "'")
    Dim str1 = e.DataTable.GetComboListString("物料编号","模具型号='" & e.DataRow("模具型号") & "'").Replace("|",",")
    Dim str2 = e.DataTable.GetComboListString("物料编号","模具型号='" & e.OldValue & "'").Replace("|",",")
   
    For Each dr As DataRow In drs1
        dr("所应用的产品") = str1
    Next
    For Each dr As DataRow In drs2
        dr("所应用的产品") = str2
    Next   
End If