How to nest more than 7 functions in Excel with If Function

Hello,

I need some help in nesting more than 7 functions in Excel with "If" function.

I have uploaded the excel sheet for your perusal.

I am trying to create a formula that when you choose the currency in Column E, the result

in Column G would be the conversion to USD, using the different conversion rates in column W which is linked to MSN money and updated automatically

Unfortunately, I have more than 7 Currencies and the If function is not accepting more.

Can you help please.

Many thanks