5 Weeks of not seeing my Grandchildren

Can anyone advise me. My only son and I used to have a great relationship prior to him getting married. The wife is rather controlling and since having their 2 children they have used them against me as in if I do not do as they ask they stop me from seeing them. This has happened 3 times (children are 4 and 2) They know me and certainly my grandaughter would have been asking after me. At our last meeting (my son and I) he pretty much abused me and said he didnt trust me with the children (although iv babysat every thursday and most saturday days for the last 2 years) Hes finding every excuse how he can justify this. I have tried contact through other people and im just ignored. Im a working professional woman (bad divorce from his father, due to his dads adultry) I need to know if i go through the courts will they try and get me to have contact with the children. I feel so sad and as if a massive part of my life is missing without the contact with the children.