Auto-Reject Journal if Attachment is Missing at Journal Batch– Approval Worksheet (Non-BPM)

Summary:

Requirement: If a journal is submitted without a file attachment at the Journal Batch/Header level, it must be automatically rejected by the workflow.

Additional Information:
No BPM Worklist access: I am restricted to using the Simplified Approval Excel Worksheet (Manage Journal Approval Rules).

Sandbox is insufficient: I have already applied the "Required" property in a Sandbox. It displays the asterisk correctly, but it is purely cosmetic and does not prevent the user from clicking 'Post' without an attachment.

No Header Attributes in Sheet: The "Journal Header" object in my workflow sheet does not show "Attachment Count" or "Attachment Exists" in the standard dropdowns.