My wife's ex-husband was in the Army when they divorced and while he was still enlisted I think his child support payment came right from his military pay. 

As somebody who has to deal with a deadbeat dad I would suggest getting the child support setup so that it is directly deposited into your daughter's checking account every month.  My wife's was like that for years until he screwed it up last summer and decided to start sending checks in the mail (he lives in Arizona) but they are usually late and one month he even forgot to sign the check he sent.  Based on what he's done so far I'm guessing he will use the child support to fight with your daughter and if it can be setup for automatic payment your daughter's and grandchild's life will be much easier.