False claim to child protective servies by ex-wife?

My husband's ex-wife has called CPS for the fourth time in four years. Everytime she and her new husband get mad at anyone, they take it out on us. EVERY single time she has called CPS they have cleared us and according to them "chalked it up to sour gs". This newest call will go the same way. My question is....can we pursue legal charges against his ex-wife for making false claims? Can this be done thru CPS? Because I know someone will ask this I will answer ahead of time.....we know it is her because everytime she has gone into a rage and gotten mad about something frivolous (like a child's item forgotten at our home she claims we are refusing to return property and calls her lawyer) we subsequently and "coincidentally" get a CPS charge filed within 3-5 days on some other issue. The latest is that we "physically abused" our kids by "playing too rough in the pool". How can we make this harment stop?