^ Spade some advice, it might be old fashioned and all that BUT, it is sound. It's called making a solution

You have a potential problem , I offer you a solution! Now obtain from the nefarious drug dealers who frequent the 'pub' you score from *
whistles and rollseyes* a 'known' amount of powder, in your case 2CB.
This next bit calls for a little imagination, we'll pretend that you actually get 1,000mgs from your dealer (I think you would get what you asked for) , dunno why , funny feeling that its gotta be a scrupulous person.

Anyway you take your 1,000mgs 2CB and dissolve it in a known quantity of water (though other solvents might be equally suitable.
If we take 1,000 mgs of powder
Also 100 millitres of water
We dissolve the powder in the water.
Our solution should now be at a concentration of 10mgs/ml
You then obtain a syringe barrel to accurately measure exactly ten milligrams or whatever dose you feel applicable to the situation.
To take this into clubs ,if you fear search, then drop it onto blotting paper not acid blotter but something innocuous like.
Good luck