We had same requirement.
In OTL we have 2 Workflows.
When you submit Timecard it fires 2 instance ie 2 item key of HXCEMP.
Depending on setup in OTL Admin you can have Auto Approval or Manager Approval or Custom Workflow Approval.
When you change this to Custom Workflow it fires HXCSAW workflow(Child of HXCEMP)
From HXCSAW you can fire custom notifications and post completion of HXCSAW flow will resume to HXCEMP.
Let me know if you need any further information.