Beta Weekly Timesheet Form Script

Hi All

I am testing the usage of beta weekly timesheets in our sandbox account.

I have run into an issue where the Copy Previous Timesheet button is not reliable.  If a job in the previous weekly timesheet is closed, it fails, if a project task is completed, it fails... It seems to just be adding the time entries field by field and if it runs into validation issues, it will just stop the process of importing the rest of the data.
In standard weekly timesheets it would simply not include the job.

To avoid this, I thought of removing the standard button via customise form, replacing it with a custom action (button) which calls a function in the client script which will then attempt to emulate the same kind of process.  The only problem is... I can't get the button to call the function using the beta weekly timesheet feature.  I tried just calling a function in my client script named "copyFromWeek" which triggers and alert but it doesn't seem to be calling it.