1、不要重置列，如果需要全部重新计算，参考

http://www.foxtable.com/webhelp/scr/2219.htm

2、如果自己不会调试，上传具体实例测试。

1、代码

Dim dr As DataRow = e.DataRow
Dim dt As DataTable = DataTables("销售开单")
If e.DataCol.Name = "编号" Then
    Dim ary1() = {"AA","BB","CC","DD","EE","FF","GG","HH","II","JJ","KK","LL"}
    Dim ary2(ary1.length) As Date
    Dim d As Date = Date.today
    d = new Date(d.year, d.month, 1)
    ary2(0) = d
    For i As Integer = 0 To ary1.length-1
        ary2(i+1) = d.AddMonths(-i-1)
    Next
    Dim ary3(ary1.length-1) As Double
    Dim drs = dt.Select("[编号] = \'" & dr("编号") & "\'", "日期 desc")
    For Each cdr As DataRow In drs
        For i As Integer = 0 To ary1.length-1
            If cdr("日期") >= ary2(i+1) AndAlso cdr("日期") < ary2(i) Then
                ary3(i) += cdr("数量")
                Exit For
            End If
        Next
    Next
    For i As Integer = 0 To ary1.length-1
        dr(ary1(i)) = ary3(i)
    Next
End If

2、代码

If MainTable.Name = "计算" Then
    systemready = False
    Dim f As New Filler
    DataTables("计算").DataRows.Clear() \'清除原有数据
    f.SourceTable = DataTables("销售开单")
    f.SourceCols = "编号"
    f.DataTable = DataTables("计算")
    f.DataCols = "编号"
    f.Fill()
    systemready = True
    DataTables("计算").datacols("编号").RaiseDataColChanged
End If