Update - Return

Hello,
I have a table in SQL database. It has three Columns: C1, C2,C3 and C4.
C1 is a PrimaryKey column. I do not know the Id(value) for C1 but I do know the value of C2 and C3. I want to update C4 and then return the Id of C1. The Row is updated correctly but the return value is always 0. I hope somebody can help me with this. Thanks.


Code Block
CREATE PROCEDURE [dbo].[MyTableUpdate]
(
@C1Id int=default,
@C2Id int,
@C3Id int,
@C4V nvarchar(50)
)
AS
if exists(SELECT * FROM MyTable WHERE (C2Id=@C2Id and C3Id=@C3Id))
begin
update MyTable SET C4V=@C4V WHERE (C2Id=@C2Id and C3Id=@C3Id)
RETURN @C1Id
end
else
begin
INSERT INTO MyTable(C2Id,C3Id,C4V)VALUES(@C2Id,@C3Id,@C4V)
Select @@Identity
end