Withdraw Request Issue

I am having an issue, When a withdrawal request is made by an instructor, the amount requested does not get reduced(before admin approves or rejects) from the amount available to withdraw. So, the instructor can send multiple withdraw requests for the available balance.

So, the when a Instructor requests a withdraw amount, the amount must be reduced from the available amount to withdraw balance. When admin approves the request, the amount must be reduced from the current balance as well. When admin rejects, the requested amount must be added to the withdrawable amount.

What do you say? I see this as a very critical issue.🙁