Calling a SP in UDF and Storing Value Return By SP In UDF

Hi EveryBody,
I need to call a Stored Procedure in a UDF.This input of SP would be a string and in turn that output Of SP would also be a string.Also i need to store the output of SP in a Calling UDF.Is it possible if Yes Please tell me How can i make It.Please help.
Thanks!!!
DheerajDECLARE @.outstring varchar(500), @.instring varchar(500)
EXEC dbo.usp_YourStoredProc @.instring,@.outstring OUTPUT
--now you can use the @.outstring in your code as you want.
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Hi Thanks for reply,
I have done this also but its giving me Error - "Only functions and extended stored procedures can be executed from within a function." .I think I have to make SP As Extended SP I dont know how to make it can you provide any kind of sample for it.It would get more clear to me.
Thanks,
Dheeraj Verma

|||rather than trying to convert a stored proc to extended stored proc you could convert your stored proc to a function, unless you have some DML statements in your function?