Tracking Of Credits (Hours) With Expiration

I work in a HR department and I'm trying to create a spreadsheet to track the amount of extra-duty hours each worker has. For every extra hour they work today, they can use this hour next time.

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This is my current spreadsheetCredit hours means hours added to their 'account'.Debit means hours taken out.Hours will expire in X days if not utilised.Right now, each worker has their own spreadsheet in the same workbook.I have about 25 workers.Is this the best way to manage this?How can I create a 'bank account' system to track their hours?

hourstracking.xlsx