Chemical to control what body part(s) inflate

Now that subjects can be inflated, I think a neat thing to do would to have a chemical that gives the user control of what body part or parts inflate before using it. 

For example, you use it on the subject, and a ui pops up showing the subject. You click on a body part, it gets highlighted to show what you've selected, then click ok. Now until the subject is given an antidote, or the chemical is used again, any form of inflation will be directed to said body part.