Problem creating a GetNextKey Stored Procedure

I am trying to create a GetNextKey stored procedure given
a tablename passed a parameter, but have had problems creating it.

Here is what I have so far:
------------------------------------------------------
CREATE PROCEDURE GetNextKey @Tablename Varchar(10)
AS

Declare @sSQLStatement Varchar(255)
        @CurKey Integer,
        @NextKey Integer
 
select @sSQLStatement = 'select @CurKey=max(prkey) from ' +@Tablename
Exec (@sSQLStatement)

select @NextKey = @CurKey + 1
----------------------------------------------------

At first I had a problem using a variable in the from
clause of an SQL statement. I got around this by building
the sql statement in a variable and executing it using
"Exec". When I did this and executed the stored proc. however, I got the following error: "Must declare variable
'@CurKey'".

I am trying to find out the following:

a) If I can use a variable in the from clause of an SQL
     statement.
b) How I can assign the value to @CurKey in the SQL     statement executed with "Exec".
c) How I can return @NextKey as the result of the stored
    procedure.
d) If someone has created a similar procedure and can show
    me ways to do it.

Thanks in advance to anyone who reads/responds to my question.