Placing Sp_executesql Data Into A Var

I have a stored procedure that takes various parameters and performs simple selects using these. A quick summary of the db structure this is working on would be :

lookup_table1
table1_id
description

lookup_table2
table2_id
description

This stored procedure attempts to select the given description from the given table and return the id, if the id isnt present it then inserts the new value and returns the new id.

Now I have this working, ish, but the problem that I have is that in the case of a new insert the procedure returns two datasets, an empty one (as the initial select returned no results) and another with the id of the newly inserted value.

This procedure as it stands right now


CREATE PROCEDURE aida_lookup
@lookup_table varchar(255),
@lookup_id_name varchar(255),
@lookup_description_col varchar(255),
@lookup_value varchar(255)
AS

declare @sql nvarchar(2048)

--
-- Check if the given lookup value exists in the give table / column
--
set @sql ='SELECT ' + @lookup_id_name + ' FROM ' + @lookup_table + ' WHERE ' + @lookup_description_col + ' = ''' + @lookup_value + ''''
EXECUTE sp_executesql @sql
if (@@rowcount = 0) goto new_value
if (@@error <> 0) goto on_error
return(1)

--
-- Insert new lookup value into the given table / column
--
new_value:
-- NEED TO CLEAR PREVIOUS NULL SELECT
begin transaction
set @sql = 'INSERT INTO ' + @lookup_table + ' (' + @lookup_description_col + ') VALUES (''' + @lookup_value + '''); SELECT SCOPE_IDENTITY()'
execute sp_executesql @sql
if (@@error <> 0) goto on_error
commit transaction
return(1)

--
-- Error handler
--
on_error:
rollback transaction
return (0)
GO



The problem being is that if the value is inserted as a new value I need to remove the empty dataset so that regardless of how the procedure is run, it will always return the id at position row 0 column 0.

My attempted solution was to declare a @temp var and place the return value of sp_executesql into this, and if it wasnt null then return it, and if it was then proceed to insert, e.g.


declare @temp int
...
SET @temp = EXECUTE sp_executesql @SQL
if (@@temp = null) goto new_value
SELECT @temp
return(1)


Obviously this doesnt work, so I am open to suggestions. To be completly honest I have run out of hair to rip out and I am sure this can probably be done in a much more elegant fashion, so any help will be greatly appreciated