Oldx and oldy would be variables you'd use to store the old position of the tilemap. They could be global variables or instance variables of the tilemap. You just have to define them.
Other than that, yeah those are the actions to position the tilemap onscreen. Except the order you do those actions is important. You need set the position of the tilemap first before pasting. Then you'd need to move the tilemap back afterwards to it's original position. Thinking about it i did forget a step, the paster object needs to be moved too.
So here's variety of the above working in the same way as your events. Instead of storing the old position it stores the position difference, and moves stuff back and forth by that.
global number dx = 0
global number dy = 0
-- paster: clear to rgba(0,0,0,0)
-- paster: set position to (player.x, player.y)
//comment// actions to paste tilemap
-- set dx to palyer.x-scrollx
-- set dy to player.y-scrolly
-- tilemap: set position to (self.x-dx, self.y-dy)
-- paster: set position to (self.x-dx, self.y-dy)
-- paster: paste tilemap
-- tilemap: set position to (self.x+dx, self.y+dy)
-- paster: set position to (self.x+dx, self.y+dy)
-- paster: set position to (120,120)