I have no experience with the VT38A so cannot help you there. As far as the macro, you could create a timer in ActiveHome Pro, but I think the lowest repeat granularity you get there is once per day. To make it repeat once per hour, you would have to create 24 daily timers, one for each hour of the day.
There is an alternative: You could install the AHP SDK from
http://kbase.x10.com/wiki/Activehome_Pro_SDK and then create a scheduled task with the Windows Task Scheduler (accessible from the Windows Control Panel) instead since the latter offers many more repeat options. This does require that the PC be on and connected to the X10 PC interface 24/7. For the action in your task, select:
Action: Start a program
Program: C:\Program Files (x86)\AHSDK\bin\ahcmd.exe (use the Browse button as your path may be slightly different)
Arguments: sendplc a5 off
The example is for a camera power supply at address a5, so change as appropriate. If you want to send an RF command to a transceiver instead, use "sendrf" in place of "sendplc".
