ALTER FUNCTION dbo.FunctionName(p1 int, p2 int) returns BIT AS 
BEGIN
 RETURN 1
END

GO

SELECT [dbo].[FunctionName] (1,2)

--- Ran this first
create function dbo.Junk(@x int)
returns int
as
begin
return @x;
end
go
--- Ran from here down in SSMS
alter function dbo.Junk(@x int, @y int)
returns int
as
begin
return @x + @y;
end
go
select dbo.Junk(1, 2);
go
drop function dbo.Junk;