Hello and thank you for contacting us. This is Dwayne B. and I’m an expert here and looking forward to assisting you today. If at any point any of my answers aren’t clear please don’t hesitate to ask for clarification. Also, I can only answer the questions you specifically ask and based on the facts that you give so please be sure that you ask the questions you want to ask and provide all necessary facts.
I'm not sure what you mean by "Will a Motion for New Trial work?"
If you mean is that the right pleading to file to raise the issue of the falsehoods with the court and request for the court to reconsider the matter, then yes that is the appropriate paperwork to file if you are still within the time limit (30 days from the date the order was signed in most states).
If you are asking if the judge will reverse his order and grant you custody because you file the Motion for New Trial then the answer is no, all that motion can do is give you an opportunity to have a new hearing and offer your evidence and contest your ex's evidence.
However, if you intend to appeal then you definitely want to file the Motion for New Trial and submit the evidence in admissible form as to the lies your ex told so that it is in the record otherwise the Court of Appeals can't even consider it.
If you don't have a lawyer then you definitely want to consider getting one at this point because there is a specific way evidence has to be offered for it to be admissible and considered by the trial court and the Court of Appeals. If the evidence is not offered correctly then it will not be considered at all.