Multiplying 2 Text Field

[Seda Atagören]

I need to calculate 2 text fields and come up with a numeric value in another field. 

The case is, i need to multiply an exchange rate of a day with the grand total value written in a text field type. 

I'm not sure if it's possible to make a calculation with two field which are not number type.

I'd be appreciated if you could answer