How To Return The Result Of An EXEC From A Function

Hi,

I am trying to find a way to return the result of an EXEC(*sqlstring*) from a function. I can return the tsql but not the result of an execute.

This is my function:

ALTER FUNCTION [dbo].[ReturnPickItemValue]
(
-- Add the parameters for the function here
@TypeID int,
@CaseID int
)
RETURNS varchar(max)
AS
BEGIN
-- Declare the return variable here
DECLARE @RTN varchar(max)

IF(SELECT IncludeDates FROM TBL_LU_PICK WHERE PickTypeID = @TypeID) = 1
BEGIN
SET @RTN = 'SELECT PickItem I +
CASE D.IsStartDateEstimated
WHEN 0 THEN CAST(StartDate as varchar)
ELSE CAST(dbo.ReturnEstimatedDate(D.IsStartDateEstimated, 0) as varchar)
END +
CASE D.IsEndDateEstimated
WHEN 0 THEN CAST(EndDate as varchar)
ELSE CAST(dbo.ReturnEstimatedDate(D.IsEndDateEstimated, 1) as varchar)
END

FROM TBL_LU_PICK L
INNER JOIN TBL_Pick_Items I ON I.PickTypeID = L.PickTypeID
INNER JOIN TBL_PICK P ON P.PickItemID = I.PickItemID
LEFT JOIN TBL_PickDates D ON D.PickID = P.PickID
WHERE L.PickTypeID = ' + CAST(@TypeID as varchar) + '
AND P.CaseID = ' + CAST(@CaseID as varchar)
END
ELSE
BEGIN
SET @RTN=
'SELECT I.PickItem
FROM TBL_LU_PICK L
INNER JOIN TBL_Pick_Items I ON I.PickTypeID = L.PickTypeID
INNER JOIN TBL_Pick P ON P.PickItemID = I.PickItemID
WHERE L.PickTypeID = ' + CAST(@TypeID as varchar) + '
AND CaseID = ' + CAST(@CaseID as varchar)
END


RETURN @RTN

END



Each time I try " RETURN EXEC(@RTN) " or something similar I get an error.

I have tried executing the tsql and assigning the result to a varchar and returning that varchar but i get an error.

Anyone with any ideas?