Years agom I did something similar with a simple DOS command line (batch file). I had my computer at work dial my home phone as a wakeup call. All I did was
ECHO >AUX: DT8185551234;
In your case, you could insert a series of commas, followed by the PIN. You might need to replace AUX with COM1:, COM2:, etc. And you can set up the repeating sequence using Task Scheduler.