Currency Conversions w/ If Statements?

This may be a bit long, but here it is:
I need help setting up a sheet with travel expenses incurred in different
countries. These expenses will be converted into Swiss Francs (CHF) and US
Dollars (USD). Columns A through E contain codes and descriptions. Column G displays USD converted values and column H, Swiss Franc, or CHF, converted values. Individual amounts are entered EITHER in column K (for Euro values),OR L (for pound - GBP values), OR in a column M for "floating" currencies, which can vary depending on what country was visited, Sweden or Russia, for example... Columns I and J repeat the Swiss franc and dollar values respectively.

Currently H2:H7 contain currency rates for the following: GBP =1CHF; 1 $= SEK; 1 $= GBP; 1 $ = CHF; 1 $ = €; 1CHF=€; which are used as absolute reference cell addresses as the placeholders for conversion rates that are updated periodically for inclusion in formulas that will be in G 10 and H10 going down with every new expense entered.

The conversion itself is simple, my question is how do I write a formula in G10 and H 10 that will allow the secretary to enter an amount, say in L10 for pounds and have the formula in G10 and H10 check that there are no values in I10, J10, and M10 and then convert the pound amount in L10 by the corresponding conversion value in H4 (in this case) for The USD in pounds. Alternatively, if an entry is made into M11 for Russian Rubles, for example, it would check that the other cells K11 and L11 don't have any values and therefore it will know to divide it s amount by the corresponding value of the ruble in H2:H7. I thought this might be achieved with If statements checking for null values. or a variation of an IF statement. Did I make this too complex? It's what we need unfortunately.

The primary objective is to have a secretary input ONLY the updated currency rates in H2:H7 and the varying amounts in K10, OR 10, OR M10 and additional rows down and have these values automatically converted by the formula in G and H to be added up at the end of all entries.

I appreciate anything you can say that will help or guide me in the right direction.

Renetrainer

It would help if you post a sample of your work

Thanks
Denis