Group subscription plan with variable price

Update
If I put a price other than zero in the subscription plan this works, but it adds this to the price which I don't want.
When I set the price to 5.99 and then tried to remove this in the query with the following it doesn't remove it.
SELECT ( (`cb_pupils` * -5.99)-5.99 ) FROM `#__comprofiler` WHERE `id` = '[user_id]'

Is my syntax incorrect?, or do I need to set up another promotion to remove the 5.99?

Regards,
Andrew

Test your raw query against your database using phpmyadmin for example to see if it displays a result as expected (be sure to replace user_id with a valid users id). This will tell you if there's an error and exactly where in your query. It also lets you adjust the query as needed until the results are as expected.

Excellent, thanks, will do that.