FM for calculation of FX rate based on reference currency

Dear experts,

I need to carry out currency conversion in a BW transformation. For this, I am using FM CONVERT_TO_LOCAL_CURRENCY which works fine. Some of my exchange rate types use reference currencies, obviously the FM does not support this. Example:

Need to convert:

AUD --> CHF

Rates are maintained for

AUD : EUR

CHF : EUR

and EUR used as reference currency for the FX rate type.

Does anybody know how I can utilize FMs to get the desired result or do I have to calculate it on my own?

Thanks for any suggestions.

BR,

G.