Recursion Using SQL User defined Function and calling scalar valued Function

GO
/****** Object:  UserDefinedFunction [dbo].[GetBudgetRoot]    Script Date: 10/03/2012 09:39:07 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:        <Author,,Gautam>
-- Create date: <Create Date, ,>
-- Description:    <Description, To Get the Root ID for Budget Components ,>
--takes Component ID (BudgetHeadID Having ParenID not null) and Returns The Root with parenID Null
-- =============================================
Create FUNCTION [dbo].[GetBudgetRoot](@CompID int)

RETURNS int
AS
BEGIN
    -- Declare the return variable here
    Declare @RootID int;
  
    -- Add the T-SQL statements to compute the return value here
    ---Scalar-valued functions may be invoked where scalar expressions are used,
    ---including computed columns and CHECK constraint definitions. When invoking scalar-valued functions,
    -- at minimum use the two-part name of the function.
    if ((select ParenID  from tbl_BudgetHeadMaster where BudgetHeadMasterID =@CompID )is not null)
    begin
    set  @RootID= (select ParenID  from tbl_BudgetHeadMaster where BudgetHeadMasterID =@CompID and ParenID is not null)
   set @RootID =    dbo.GetBudgetRoot(@RootID)
  
    end
    else
    begin
    set @RootID= @CompID
  
    end


    RETURN @RootID;

END

---To Call

Declare @ID int
set @ID= dbo.GetBudgetRoot(119)
select @ID