At the moment JForex-API does not support String values as indicator parameters. For now consider modifying the following lines in the source to get the desired time frames (note that in JForex the time values are always represented in GMT):
extern string StartTime = "18:00";
extern string EndTime = "17:45";
There seems to be a time conversion issue - a 12 hour lapse - this will be fixed with the next converter versions.