Thank you for your quick answer.
I got a solution from your hint and sample code..
I used olap_updated event.
For other developer’s reference, here is real code.
Dim olap = OlapSales.OlapEngine
Dim dt = olap.OlapTable
Dim iDiscRateIdx, iOrgAmtIdx, iDiscAmtIdx As Integer 'for Discount Rate
iDiscRateIdx = -1
iOrgAmtIdx = -1
iDiscAmtIdx = -1
For i = 0 To dt.Columns.Count – 1
' Discount Rate calculation.
If dt.Columns(i).ColumnName.Contains("S_DISC_RATE") Then
iDiscRateIdx = i
End If
If dt.Columns(i).ColumnName.Contains("S_ORG_AMT") Then
iOrgAmtIdx = i
End If
If dt.Columns(i).ColumnName.Contains("S_DISCOUNT") Then
iDiscAmtIdx = i
End If
If iDiscRateIdx <> -1 And iOrgAmtIdx <> -1 And iDiscAmtIdx <> -1 Then dt.Columns(iDiscRateIdx).Expression = String.Format("[{1}] / [{0}]", dt.Columns(iOrgAmtIdx).ColumnName, dt.Columns(iDiscAmtIdx).ColumnName)
iDiscRateIdx = -1 ' Reset
iOrgAmtIdx = -1
iDiscAmtIdx = -1
End If
Next