Looks like I didn't need two query fields as your second query option worked, I just had to change ( `cb_gvp` * 0.035 ) to ( `cb_gvp` * -0.00035 ) to calculate the GVP field x 0.035% e.g.
SELECT ( `cb_gvp` * -0.00035 ) FROM `#__comprofiler` WHERE `id` = '[user_id]'
Without the -0.00035 it would reduce the amount, having "-" in the query results in a positive, not negative amount, confusing, but it works.
Thank you for your sample query formulas as I found it difficult to find any other CB query examples for this variable membership subscription requirement.
This is working great now.
Thank you!
