Problem Creating Function To Be Schema Independent

I am writing a SQLServer script that I want to be schema name independent. I mean I know that all users of the script will have the same tables, but not necessarily the same schema name.

When I hard code the script to use the name of my schema, wcadmin, it works OK.

CREATE FUNCTION wcadmin.dectohex(@a numeric)
RETURNS varchar(8)
BEGIN
DECLARE @x varchar(8)
DECLARE @y varchar(1)
DECLARE @z numeric
DECLARE @w numeric

SET @w=@a
SET @x=''

WHILE @w > 0
BEGIN
SET @z = @w % 16;

SET @y= CASE @z
WHEN 10 THEN 'A'
WHEN 11 THEN 'B'
WHEN 12 THEN 'C'
WHEN 13 THEN 'D'
WHEN 14 THEN 'E'
WHEN 15 THEN 'F'
ELSE CAST(@z AS varchar)
END

SET @w = ROUND(@w/16,0,1)
SET @x = @y + @x
END

-- Pads the number with 0s on the left
SET @x = RIGHT(REPLICATE('0',8) + @x ,8)
RETURN @x
END;
GO

select 'WTDOCUMENT' HOLDER,
dm.WTDocumentNumber ITEMNUMBER,
dm.name ITEMNAME,
ad.fileName ContentFilename,
fh.hostName VaultHost,
wcadmin.dectohex(fi.uniqueSequenceNumber) VaultFile,
fm.path VaultPath
from
WTDocument di,
WTDocumentMaster dm,
HolderToContent hc,
ApplicationData ad,
FvItem fi,
FvFolder ff,
FvMount fm,
FvHost fh
where di.idA3masterReference = dm.idA2A2
and fm.idA3A5 = ff.idA2A2
and fm.idA3B5 = fh.idA2A2
and fi.idA3A4 = ff.idA2A2
and ad.idA3A5 = fi.idA2A2
and hc.idA3B5 = ad.idA2A2
and hc.idA3A5 = di.idA2A2

DROP FUNCTION wcadmin.dectohex;
GO

But when I remove my schema name I get the error

'dectohex' is not a recognized built-in function name.

In this case I'm just using :-

CREATE FUNCTION dectohex(@a numeric)
.
.
.
.
select 'WTDOCUMENT' HOLDER,
dm.WTDocumentNumber ITEMNUMBER,
dm.name ITEMNAME,
ad.fileName ContentFilename,
fh.hostName VaultHost,
dectohex(fi.uniqueSequenceNumber) VaultFile,
.
.
.
.
DROP FUNCTION dectohex;

Creating and dropping the function seems to work OK when I drop the schema name, I just can't call it.

I've been trying various permutations of dbo and [dbo] prefixes unsuccessfully.

Any suggestions?

Thanks


David