In Internet Explorer, I have a form with three test input fields.
I need that thir field will display sum of two previous fields.
I know that this can be done by using

f3.setExpression( 'value', 'f1.value+f2.value' )

in form onload event.

However, I need to set dynamic value property directly in f3 without script.

MS KB says I can use dynamic expression for value property, but the following code will not work. How to implement this ?
Remove spaces after < character in the following code.

Field1 < input name=f1 >
Field2 < input name=f2 >
Sum < input name=f3 value=javascript:"return f1.value+f2.value;" >