Public Function EvaluateExpression( _
   ByVal row As Integer, _
   ByVal column As Integer, _
   ByVal expression As Expression _
) As Object

Dim instance As DefaultSheetDataModel
Dim row As Integer
Dim column As Integer
Dim expression As Expression
Dim value As Object
 
value = instance.EvaluateExpression(row, column, expression)

public object EvaluateExpression( 
   int row,
   int column,
   Expression expression
)

FarPoint.CalcEngine.Expression ex;
FarPoint.Win.Spread.Model.DefaultSheetDataModel dataModel = new FarPoint.Win.Spread.Model.DefaultSheetDataModel(10, 10);
dataModel.AddCustomName("TWICESUM", new FarPoint.CalcEngine.DoubleExpression(10));
dataModel.SetFormula(1, 1, "TWICESUM");
fpSpread1.ActiveSheet.Models.Data = dataModel;
ex = dataModel.GetExpression(1, 1);
dataModel.EvaluateExpression(1, 1, ex);
MessageBox.Show("The expression is " + ex.ToString());

Dim ex As FarPoint.CalcEngine.Expression
Dim dataModel As New FarPoint.Win.Spread.Model.DefaultSheetDataModel(10, 10)
dataModel.AddCustomName("TWICESUM", New FarPoint.CalcEngine.DoubleExpression(10))
dataModel.SetFormula(1, 1, "TWICESUM")
FpSpread1.ActiveSheet.Models.Data = dataModel
ex = dataModel.GetExpression(1, 1)
dataModel.EvaluateExpression(1, 1, ex)
MessageBox.Show("The expression is " & ex.ToString())