Using A Scalar Valued Function As A Parameter Of A Table Valued Function?

Ok, I'm pretty knowledgable about T-SQL, but I've hit something that seems should work, but just doesn't...

I'm writing a stored procedure that needs to use the primary key fields of a table that is being passed to me so that I can generate what will most likely be a dynamically generated SQL statement and then execute it.

So the first thing I do, is I need to grab the primary key fields of the table.  I'd rather not go down to the base system tables since we may (hopefully) upgrade this one SQL 2000 machine to 2005 fairly soon, so I poke around, and find sp_pkeys in the master table.  Great.  I pass in the table name, and sure enough, it comes back with a record set, 1 row per column.  That's exactly what I need.

Umm... This is the part where I'm at a loss.  The stored procedure outputs the resultset as a resultset (Not as an output param).  Now I want to use that list in my stored procedure, thinking that if the base tables change, Microsoft will change the stored procedure accordingly, so even after a version upgrade my stuff SHOULD still work.  But... How do I use the resultset from the stored procedure?  You can't reference it like a table-valued function, nor can you 'capture' the resultset for use using the  syntax like:

DECLARE @table table
@table=EXEC sp_pkeys MyTable

That of course just returns you the RETURN_VALUE instead of the resultset it output.  Ugh.  Ok, so I finally decide to just bite the bullet, and I grab the code from sp_pkeys and make my own little function called fn_pkeys.  Since I might also want to be able to 'force' the primary keys (Maybe the table doesn't really have one, but logically it does), I decide it'll pass back a comma-delimited varchar of columns that make up the primary key.  Ok, I test it and it works great.

Now, I'm happily going along and building my routine, and realize, hey, I don't really want that in a comma-delimited varchar, I want to use it in one of my queries, and I have this nice little table-valued function I call split, that takes a comma-delimited varchar, and returns a table... So I preceed to try it out...

SELECT *
FROM Split(fn_pkeys('MyTable'),DEFAULT)

Syntax Error.  Ugh.  Eventually, I even try:

SELECT *
FROM Split(substring('abc,def',2,6),DEFAULT)

Syntax Error.

Hmm...What am I doing wrong here, or can't you use a scalar-valued function as a parameter into a table-valued function?

SELECT *
FROM Split('bc,def',DEFAULT) works just fine.

So my questions are:

Is there any way to programmatically capture a resultset that is being output from a stored procedure for use in the stored procedure that called it?

Is there any way to pass a scalar-valued function as a parameter into a table-valued function?

Oh, this works as well as a work around, but I'm more interested in if there is a way without having to workaround:

DECLARE @tmp varchar(8000)

SET @tmp=(SELECT dbo.fn_pkeys('MyTable'))

SELECT *

FROM Split(@tmp,DEFAULT)