For any orders extending a caveat to be effective, not only must they be entered forthwith with the court, but they must be lodged with the Register General's office – Land & Property Information.
From a family law perspective With family law property proceedings there is a duty of ongoing full and frank financial disclosure. It must be considered that post separation windfalls from inheritances or lottery wins can be excluded or taken into consideration in under s79 of the Family Law Act, particularly 79(4)(a) – (c) (s79 is for married, s90SM for de facto)
It is arguable that you do not have a direct caveatable interest in the estate of the Ex’s mother which includes the real property. But rather the proceeds from the execution of the will to the benefit to your ex, and impact upon financial resources.
I would strongly suggest seeking professional legal advice on this issue.