Scratch

I'm just getting started with Scratch, so bear with me.

As I stated before, I'm new, so I'm not really good with writing out my script on here in scratchblocks, so I will just write it out normally.

So here is my script:

When I receive StartGame
go to x: 240 y: -145
switch to costume costume1
if > touching sprite1
forever
stop script
else
forever
{switch to costume costume1
glide 5 secs to x: -240 y: -145
wait 0.1 secs
switch to costume costume2
glide 5 secs to x: 240 y: -145}

The part I put in curly braces is the part I need to stop when my costume1 touches sprite1, but before costume1 touches sprite1, I need costume1 to glide back in forward forever until it touches sprite1, or sprite1 touches it.

It would be awesome if someone could help
Thank you