Defining value for time cron from item value

Trying to create a settings page for my outdoor lighting.
Would it be possible to do the following ? (or something similar)

rule "turn on outdoor lights"
 Time cron ctrl_ude_timer1_on_cron.state.toString
  sendCommand(ude_fordoer, ON)

Item ctrl_ude_timer1_on_cron would need to be a cron string of course.

Unfortunately that is not possible.

While taht exact thing isn’t possible, check here for examples of using alarms and timers. This way you can control the timings from a “settings page” and have the lights trigger at specific times.