Formula to return a text string from a reference ID

I have a data using an employee ID number rather than a name, when reporting I am trying to have the name text string appear instead of the employee refID.

e.g. John Smith is employee 125
(in all reporting data he is referred to only as 125)

I have a list of employee names and the refID they have.

I feel like this should be (and probably is) really simple but I cannot for the life of me get any formula I try to return the name!

I am actually working in SAP Crystal Reports and generally the data will link automatically for me. All the same rules apply from excel and I will only need to do it once, so I can save it as a subReport. If I don't work it out soon I'm desperate enough to concatenate the two cells and then remove the number component which will just be embarrassing if anyone ever notices! haha

I know as soon as someone tells me how to get the correct formula I will feel even more ridiculous for not being able to do it but PLEASE HELP!!

Thank you

Tegan

Thanks for the welcome, I'm sure this forum will save me a lot of frustration!

And thank you so much! Exactly what I needed, worked a treat! You've made my Monday far less painful