Public Sub SetFormula( _
   ByVal row As Integer, _
   ByVal column As Integer, _
   ByVal value As String _
) 

Dim instance As SheetView
Dim row As Integer
Dim column As Integer
Dim value As String
 
instance.SetFormula(row, column, value)

public void SetFormula( 
   int row,
   int column,
   string value
)

public class CubeFunctionInfo : FarPoint.CalcEngine.FunctionInfo
    {
      public override string Name { get { return "CUBE"; } }
      public override int MinArgs { get { return 1; } }
      public override int MaxArgs { get { return 1; } }
      public override object Evaluate (object[] args)
      {
        double num = FarPoint.CalcEngine.CalcConvert.ToDouble(args[0]);
        return num * num * num;
      }
    }

fpSpread1.AddCustomFunction(new CubeFunctionInfo());
fpSpread1.ActiveSheet.SetFormula(1, 1, "CUBE(4)");

Public Class CubeFunctionInfo
   Inherits FarPoint.CalcEngine.FunctionInfo

   Public Overrides ReadOnly Property Name() As String
     Get
       Return "CUBE"
     End Get
   End Property

   Public Overrides ReadOnly Property MinArgs() As Integer
     Get
       Return 1
     End Get
   End Property

   Public Overrides ReadOnly Property MaxArgs() As Integer
     Get
       Return 1
     End Get
   End Property

   Public Overrides Function Evaluate(ByVal args() As Object) As Object
       Dim num As Double = FarPoint.CalcEngine.CalcConvert.ToDouble(args(0))
       Return num * num * num
   End Function
End Class

FpSpread1.ActiveSheet.AddCustomFunction(New CubeFunctionInfo)
FpSpread1.ActiveSheet.SetFormula(0, 0, "CUBE(4)")