i have a few queries regarding application.ontime function

my macros are of the form as follows:
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1. what is the 4rth argument schedule for ?
2. can i use 2 or more macros with ontime function on the same workbook, will they interfere in each others working
3. i want the macros to stop working at say 5 o clock in the evening. how can i do that.
4. when i close my excel files i want all macros to stop. how can i do that?