The country singer, 51, revealed that his daughter and future son-in-law are planning on having not one but three wedding ceremonies, reported Us magazine.
Liam and Cyrus became engaged after dating for three years.
"Liam asked if he could have my daughter's hand in marriage, and I said yes if I could be in his brother's next movie," Billy joked of Thor actor Chris Hemsworth.
"Now, they are going to have three weddings, so I'm thinking one movie with Chris, then we got the sequel to Liam's new movie (Hunger Games: Catching Fire) coming out. They have got three weddings, that has to be three movies for me," he added.
While Billy said he doesn't know when any of those bashes might be, he is looking forward to walking Cyrus down the aisle.
"I actually sent her a note just last night that I do look forward to that moment whenever that time is," he said,