How make a text with variables

Hello again.

At the end of a process of booking a hotel need to send a mail to the end customer with the booking confirmation.
I have a pre-defined text (but can be changed) with the following format:
Booking nº @numres
Check-in: @datent
Check-out: @datsai

Is there any way I can replace the variables for their content?
The objective is the text look like this:
Booking nº 2748
Check-in: 05/20/2016
Check out: 05/25/2016

I have tried in various ways using the STRING comand and UNSTRING with the INSPECT but still could not reach the final format

Thanks

Best Regards

Alberto Ferraz