All currency functions in MarketXLS need Source currency Symbol and the target currency symbol. Always, 1st symbol is the source and the second is symbol.
In the FX_Convert function provide the value to convert first and then provide the source and the target currency symbols.
=Fx_Ask(“USD”,”GBP”) – This will get the current Ask Price of USD to GBP
=Fx_Bid(“USD”,”GBP”) – This will get the current Bid Price of USD to GBP
=Fx_Convert(100,”USD”,”GBP”) – This will convert 100 USD to GBP