running macro on time not working

I have tried 3 different ways to run a macro on time and all have done the same thing. the macro runs 2,3 or even 4 times when it executes.
when I run the macro alone it works fine. when I run with just one line of code to start the macro it also works ok. but when I try to run more then one line to execute the macro the macro runs multipull times. Can any one fix this for me??

Application.OnTime ("07:05:00"), "macro1"
Application.OnTime ("07:09:00"), "macro1"
Application.OnTime ("07:10:00"), "macro1"
Application.OnTime ("07:12:00"), "macro1"