So let me understand... you want to speak a command that sets a timer for a specified interval, and at the end you want what? A voice telling you the timer has expired? Do you want a serial countdown at, for example, 5 mins, 2 mins 1 min and 30 seconds? This is all pretty easy with BVC actually.
Tell me your need and I'll try and post a macro for you that will do that. Remember that the simpler the command in voice the better the chance of recognition. (e.g. Your voice command is in blue, the BVC computer voice response in in red:
Computer: Yes Glor, what can I do for you? ; Timer : How long would you like me to set the timer for? ; 10 minutes ; The timer is set and countdown has started : There are 5 minutes remaining : There is one minute remaining : There are 30 seconds remaining ; 10 minutes has expired, time is up.)
For those reading and lurking, if you have not experimented with voice control you really are missing out on some of the most exciting part of HA today, and Bill's Voice Command or BVC is a terrific start, and very reasonably priced for what it offers.