Calculating the value in a form field?

Calculating the value in a form field?

Hi I need some help. I'm new to Zoho and the language used within forms (I'm a VB man normally). I've worked out a few of the functions but I can't work out what must be really simple to do but it's frustrating me!

I have a field that I want users to enter a number into.

I have another field that will be disabled for user input, but I want this to represent a value which is a multiple of the user input filed.

E.G. User input field - User would enter a number (e.g. 5). There will then be a summary field that would represent the value in that field times by 10, so this field should show '50'.

What's the right way of doing this please?

Thanks

Paul