i have a few queries regarding application.ontime function

my macros are of the form as follows:
sub macro1
'do something-something
run = now + timeserial( 0, 1, 0)
application.ontime run,"'"& thisworkbook.name & "'!macro1",false
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?