参考
Dim dt As DataTable = DataTables("表B")
For Each dr As DataRow In dt.Select("第六列 is null and 第一列 is not null")
Dim sum = val(dr("第五列"))
Dim lj As Double = 0
If sum > 80000 Then
Dim dr1 As DataRow = dt.AddNew
dr1("第一列") = dr("第一列")
Dim v = rand.Next(0, sum*100)
dr1("第五列") = v / 100
lj += v / 100
dr1("第六列") = dr("_Identify")
Dim dr2 As DataRow = dt.AddNew
dr2("第一列") = dr("第一列")
v = rand.Next(0, (sum-lj)*100)
dr2("第五列") = v / 100
lj += v / 100
dr2("第六列") = dr("_Identify")
Dim dr3 As DataRow = dt.AddNew
dr3("第一列") = dr("第一列")
dr3("第五列") = sum - lj
dr3("第六列") = dr("_Identify")
ElseIf sum > 40000 Then
Dim dr1 As DataRow = dt.AddNew
dr1("第一列") = dr("第一列")
Dim v = rand.Next(0, sum*100)
dr1("第五列") = v / 100
lj += v / 100
dr1("第六列") = dr("_Identify")
Dim dr3 As DataRow = dt.AddNew
dr3("第一列") = dr("第一列")
dr3("第五列") = sum - lj
dr3("第六列") = dr("_Identify")
Else
Dim dr1 As DataRow = dt.AddNew
dr1("第一列") = dr("第一列")
dr1("第五列") = dr("第五列")
dr1("第六列") = dr("_Identify")
End If
Next