Changing Country Currency in Form Field

I have a situation where deposits are received in both USD and KRW, and there are both "USDCurrency" fields and "KRWCurrency" fields (set with currency symbol) under the description column immediately below the field where the desosit source is identified.  An entry is made in either the USDCurrency field or KRWCurrency field, but never both (one always remains blank).  However, the voucher has multiple line items, and there's a separate subtotal column on the form with "SubAmount" fields (i.e SubAmount1, SubAmount2, etc.).

Is there a way to export the results entered either into USDCurrency field or KRWCurrency field to a single "SubAmount" field AND display the corresponding currency symbol?  USD field has decimal point and KRW field does not.

Additionally, can the "SubAmount" field that displays those results be formatted to allow the exported results be modified (i.e. not changing currency symbol, but amount of currency - for example, being able to change $100.23 to $100.24)?

Alternatively, my only thought is to enter two "SubAmount" fields (i.e. SubAmount11 formatted for USD, and SubAmount12 formatted in KRW immediately below it) for each line item in the subtotal column and manually re-enter the data and adjust amounts accordingly (not much extra work), but the form would look more nice if the subamount field lined up straight across the form as the other fields.