Access 2010 Calculated Field

Hello Experts,

I built my first access database ever for my workplace which is a currency exchange database, and I had it working well. But, the manager wanted more currency types that we could change, which has broken my database.

Basically, my access database was built on iif statements. Toggle buttons on a form set the selected currency type in number form. From there a calculated field in a table would set the exchange rate (the multiplier), and another calculated field would work out the exchanged amount (currency from * exchange rate). The calculated field for the exchange rate was something like

iif([SelectedCurrencyType]=1,0.8,(iif([SelectedCurrencyType]=2,1.2,(iif([Selected.....

and so forth. This worked well, but i found that once i had over 9 different iif statements, access would tell me that the calculated field was too complex.

I have 12 different transaction types. How can i get around this problem?

I need to pick a button on a form, to set an exchange rate (or multiplier). Access will then carry out the following calculation: Currency from * exchange rate = currency to.

Thanks in advance,

jpoppi