Calculating data in textboxes

Hi,

If I need to show the sum of 4 textboxes in a 5th textbox underneath them in my form, is there a way I can do that?

Thanks

Thank you. Also, is there any built-in function I can use to count the business days in a given date range?

[quote=Zack]Yes you can. You can use a Data Flow on the Form to count the sum of the first 4 textboxes and display that on the 5th.[/quote]

Im sorry, is there has any examples or documents that I can follow the steps to achieve this job?
I also need to calculate multiple textboxes and check by rules.
Thank you!
[i]edited by Milk on 8/2/2017[/i]