Validation of time off request Workflow approval status in Business Rule

[Arunsuresh]

Hi experts

Need to quick advise/suggestion,

We have a requirement, on Unpaid Leave. 

Requirement:- Unpaid leave has to applied when a user exhaust his/her annual leave balance. If a person is applying for "Unpaid Leave", system should validate certain checks as,

1. Annual leave balance has to be "0" when "Unpaid Leave" is requested

2. Initiated "Annual Leave" request has to be in "Approved" Status when "Unpaid Leave" is requested. 

If both conditions are not true then system should through error and "Submit" button has to be greyed out else user can submit the request. 

We could able to configure the validation on annual leave balance check but we couldn't able to validate the "Annual Leave" historical transactions to validate the approval status when "Unpaid Leave" is applied.

Looking forward for suggestion, is it feasible to configure?

Thanks

Arun