Setup PO Approval Limit in Foreign Currency

Dear Expert,

I have this question below:

In my organization, the PO approval matrix limit is set using US Dollar across entities. We had around 25 entities across the world (25 ledgers)

In oracle system, the approval matrix limit is always set at functional currency.

If we are using oracle standard, then we will need to change the approval limits based on exchange rate fluctuations every 3 months for each ledger.

Is there any other solution if i want to set it as US dollar instead of functional currency?

or anybody can share the workaround if you have similar case?

Thanks.