It shall be unlawful for any employe to receive compensation under this act if he is at the same time receiving workers' compensation under the laws of the Federal Government or any other state for the same injury. Further, it shall be unlawful for an employe receiving compensation under this act simultaneously from two or more employers or insurers during any period of total disability to receive total compensation in excess of the maximum benefit under this act. Nothing in this section shall be deemed to prohibit payment of workers' compensation on a pro-rata basis, where an employe suffers from more than one injury while in the employ of more than one employer: Provided, however, That the total compensation paid shall not exceed the maximum weekly compensation payable under this act: And, Provided further, That any such pro rata calculation shall be based upon the earnings by such an employe in the employ of each such employer and that all wage losses suffered as a result of any injury which is compensable under this act shall be used as the basis for calculating the total compensation to be paid on a pro rata basis.