I was just helped recently on this topic so i'll pass on the advice i was given.
The best way to do it but not neccesarily the cheapest is to buy a HCG kit from bacteriostatic-water.co.uk. For about £20 you get 30 slin pins/5x10ml sterile vials/30ml BA. With this kit you could do the following;
1. Draw 1ml of BA and inject into the original HCG vial , now you have 2000iu/ml.
2. Now draw the HCG solution and transfer to one of the sterile vials.
3. Next draw 4ml of BA, inject into sterile vial with HCG solution and mix gently. Now you have 5ml of HCG solution @ 400iu/ml so 200iu is 0.5ml or 0.5cc
A more simple way to do this just using one 2ml syringe/2ml of BA and is as follows;
1. Mix 1ml of BA with HCG in original vial.
2. Draw the HCG solution into a 3ml syringe (or larger).
3. Using the same syringe draw another 1ml of BA. Now you have 2ml of HCG @ 1000iu/ml so 200iu is now 0.2ml or 0.2cc. You will use this syringe to store your HCG in.
4. To use the solution just remove the needle from the 2ml syringe and use a slin syringe to draw from the top.
I believe shelf life for constituted HCG is about 60 days however it must be refrigerated.
Hope this helped.