[REBOL] Varibles in strings?

[dlawlor]

Hello, I know I've seen how to do this somewhere but can't remember for the
life of me.  I need to know how to include a variable in a string.  

Example:
Message {Active stocks for exchange (where exchange is a variable)
Toronto (Another variable containing market data)
Rest of message body included below}

All variables contain strings and numbers.  
Thanks in advance for any help.

Doug