"How do I..." Excel Help?

This is going to be confusing because i'm not even too sure what i'm asking about, but here i go. On excel how do you make it so if you put something (example 't') it would then change to something else (a tick). So if i needed to insert a tick I would just have to put t in the cell and then it would automatically make a tick...

Please let me know ASAP because i need it for some work i am doing (it would make life so much easier)