Excel-Visual Basic UserForm Coding

Been trying to do a VBA Excel sheet that calculates the cost of a pizza by size with x toppings. I have made a command button that calls a userform that lets the user select the size and toppings that the person wants. What im stuck on is getting the toppings added with the size the user selected to print to the messagebox, it prints just whatever the size of the pizza is right now. I also need to get the message box to tell the user what toppings they selected as well as the size, with the option to cancel the order but i think i can do that with an if-else statement. I just need help with the whole computation part. ill include the spreadsheet.