Как вариант но можно и через IRow или IFeature
Dim pCursor As ICursor
Dim pQueryFilter As IQueryFilter
Set pQueryFilter = New QueryFilter
Set pCalc = New Calculator
'Set pCursor = pFeatClass.Update(Nothing, True)
If (pTableSel.SelectionSet.Count > 0) Then
pTableSel.SelectionSet.Search pQueryFilter, True, pCursor
Else
Set pCursor = pTable.Search(pQueryFilter, True)
End If
With pCalc
Set .Cursor = pCursor
.Expression = 1
.Field = "Area"
End With
pCalc.Calculate