Because you're using RMXP, you'll need to play with switches.

Basically:

Hero steps onto an event. That event stops him from moving, and turns on a switch. Meanwhile there's a second event just out of site (parallel process) that uses a conditional branch to check if the switch is on. If it IS then that event comes to action.

If you can work out the code from that, then well done. I don't have the time to do it right now, and the computer I'm on only has RM2K3. If someone hasn't answered by the time I get on RMXP, then I'll post the code for each event.