Macros using dynamicdata possilble?

[alinabal]

Im trying to setup either a macro or a button in a new custom window to reply to the last person to send me a tell, with a dynamicdata variable. Im trying this so that I can tell ppl when Mana Flow is back up, using SpellInfo.Bank_5.Key_12.ReuseSec

Ideally, this

/tell %rt Mana Flow down, youll get it in %SpellInfo.Bank_5.Key_12.ReuseSec% seconds

Any ideas how to do this, either in a macro or with a custom window?

tia