Tres Cruces is the name of the bus station in Montivideo.
Their online site offers a simple form you can fill out to find routes to Argentina and Brazil as well as estimated ticket cost.
A new page will open showing a timetable of route options.
Click: “Calcular el precio estimado del pasaje” on the top left.
Boxes appears where you enter the estimated kilometers you will travel. Distances are on the timetable. Shows the price in Urugayan Pesos.