SQL 2005 - Variant Parameter Question - sql-server-2005

Question

I am working on a function that will be used by no less than 10 SProc's, and will probably grow once it is ironed out.
Problem i am running into is that i do not want to develop a function for each Data Type, which is why the SQL_VARIANT data type is looking pretty convenient for the action. I know is can do the ISNULL check on the data type but i also want to check to see if the Value being passed is a valid Number but the ISNUMERIC function does not work with SQL_VARIANT and I'm not too sure about the SQL_VARIANT_PROPERTY function.
Code so far:
CREATE FUNCTION dbo.mpt_Format_Number
(
#value SQL_VARIANT
, #money BIT
)
RETURNS VARCHAR
AS
BEGIN
--Check for NULL value
IF ISNULL(#value) BEGIN
-- Value IS NULL, return NULL
RETURN NULL
END ELSE BEGIN
-- Value is NOT NULL
DECLARE #TMP VARCHAR
END
END

Answer 1

CREATE FUNCTION dbo.mpt_Format_Number
(
#value SQL_VARIANT
, #money BIT
)
RETURNS VARCHAR
AS
BEGIN
--Check for NULL value
IF #value is null
-- Value IS NULL, return NULL
RETURN NULL
ELSE
BEGIN
-- Value is NOT NULL
if isnumeric(convert(varchar(max), #value)) = 1 RETURN 'Y' -- is valid number
--DECLARE #TMP VARCHAR
END
return 'N' --is not valid number
END
You can always test the property type with this syntax. Should be easy to incooperate in your function.
declare #t SQL_VARIANT
set #t = '3'
select SQL_VARIANT_PROPERTY(#t, 'basetype')
Result:
varchar

Answer 2

As a final implementation here is the full function as it was used.
ALTER FUNCTION [dbo].[_mpt_Format_Number]
(
#value SQL_VARIANT
, #money BIT = 0
)
RETURNS VARCHAR(max)
AS
BEGIN
DECLARE #ret VARCHAR(MAX)
--Check for NULL value
IF #value IS NULL BEGIN
-- Value IS NULL, return NULL
SET #ret = 'NULL'
END ELSE BEGIN
-- Value is NOT NULL
--Check for Numeric Value
IF ISNUMERIC(CONVERT(VARCHAR, #value)) = 0 BEGIN
--Value is NOT a Number, return NULL
SET #ret = 'NULL'
END ELSE BEGIN
--Value IS a Number
declare #isNeg BIT
declare #tmp varchar(max)
set #tmp = convert(varchar(max), round(cast(#value as money), 0), 1)
--Check if value is negative
if #value < 0 begin
--Value is Negative
set #isNeg = 1
--Remove the negative sign
set #tmp = replace(#tmp, '-', '')
end
--Remove the decimal plus any digits to the right of the decimal
set #tmp = left(#tmp ,len(#tmp) - 3)
--Is money set to True
if #money = 1 begin
--Pre-pend the dollar sign to value
set #tmp = '$' + #tmp
end
--Is isNeg set to True
if #isNeg = 1 begin
--Encapsulate the value with parenthesis
set #tmp = '(' + #tmp + ')'
end
SET #ret = #tmp
END
END
RETURN #ret
END