How To Retrieve The Result From A Stored Procedure That Executes A Dynamically Built Up Sql Query?

We have a sort of complex user structure in the sense that depending on the type of user the data resides in different tables. Therefor I needed a stored procedure that finds out what table to look for a certain column in. Below is such a stored procedure and it works like it should but my problem is that I don't know how to retrieve the result (which should be a string so can't use RETURN).

I've tried using an OUTPUT variable but since I just run EXEC (@statement) in the end I can't really set an output variable the common way (as in EXEC @outputVariable = PMC_User_GetUserValue(arg1, arg2..)) or can I?

I have also tried to use SELECT to catch the result somehow but no luck and Google didn't help either so now I'm hoping for one of you... Notice that you don't have to bother about much of the code except for the end of it where I want it to return somehow or figure out a way to call this stored procedure and retrieve the result.

Thanks in advance
ripern

-- Retrieves the value of column @columnName for credential id @credID
ALTER PROCEDURE [dbo].[PMC_User_GetUserValue]
@credID int,
@columnName nvarchar(50)
AS

DECLARE @userDataTable nvarchar(50)
DECLARE @userDataID int
DECLARE @statement nvarchar(500)
SET @statement = ' '

SET @userDataID =
(SELECT PMC_UserMapping.fk_userDataID
FROM PMC_UserMapping
INNER JOIN PMC_User ON PMC_UserMapping.fk_user_id = PMC_User.id
WHERE PMC_User.fk_credentials_id = @credID)

SET @userDataTable =
(SELECT PMC_UserType.userDataTable
FROM PMC_UserType
INNER JOIN PMC_UserMapping ON PMC_UserType.id = PMC_UserMapping.fk_usertype_id
INNER JOIN PMC_User ON PMC_UserMapping.fk_user_id = PMC_User.id
WHERE PMC_User.fk_credentials_id = @credID)

SET @statement = 'SELECT ' + @columnName + ' AS columnValue FROM ' + @userDataTable + ' WHERE id=' + convert(nvarchar, @userDataID)

-- Checks whether the given column name exists in the user data table for the given credential id.
IF EXISTS ( SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME=@userDataTable AND COLUMN_NAME=@columnName )
BEGIN
EXEC (@statement)
END