help with mathematical operators

Hi,

I'm editing forms and note that inserting basic mathematical calculation are easy in a text field (sum, etc...), but how about some more complex operations?

I'm really not a javascript editor geek and am a bit lost.

What I need is this :

first text field : automatic calculation 60% of final value       (field * 0.6)

second text field : automatic calculation 40% of final value   (field * 0.4)

third text field : final value  (addition of first two fields)

Is this possible?

thanks