using amember for software subscription

Alex,

I have software for download.
I'm using amember to control subscription for that software.

I added the custom field "license" which is the license number for the software randomly generated when they install it.

I want to do a check every time they launch the software, to see if the license number is from a active and fully paid member, or not.

Here is what I have so far:
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SELECT member_id FROM `members` WHERE data LIKE '%$license%'

Save that $memberid

SELECT completed FROM `payments` WHERE member_id = '$memberid" product_id = '$productid' AND product_id = '1' AND expire_date > now()

if the result is 1, it's active, if not, then it's not active for that product.
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Is this the best way to go about it ?
Or can you think of a more efficient or easier way to achieve this.

NL