# Predetermined mask for fields? **URL:** https://community.glideapps.com/t/predetermined-mask-for-fields/34995 **Category:** Ask for Help **Created:** [November 24, 2021, 8:38am UTC](https://community.glideapps.com/t/predetermined-mask-for-fields/34995 "2021-11-24T08:38:11Z") **Posts on this page:** 1 **Showing post:** 4
### Author: ![ThinhDinh](https://sea2.discourse-cdn.com/flex002/user_avatar/community.glideapps.com/thinhdinh/32/49_2.png) [@ThinhDinh](https://community.glideapps.com/u/ThinhDinh) #### Post date: [November 24, 2021, 11:25pm UTC](https://community.glideapps.com/t/predetermined-mask-for-fields/34995/4 "2021-11-24T23:25:34Z")
I assume you want to display it like that in your app as well and not just for the Sheet, so my proposal is as below: - Build a custom form: > [@How do I create a custom form?](https://community.glideapps.com/t/how-do-i-create-a-custom-form/25014/): > > I’m just dropping this here so I have something to refer people to when they ask. This is a simple concept app (copyable), that demonstrates the following techniques: Building custom forms for adding and editing list items (as an alternative to the native forms provided by Glide) Preventing duplicate new entries using [User Specific Columns](https://docs.glideapps.com/all/reference/data-editor/user-specific-columns) and [Relations](https://docs.glideapps.com/all/reference/data-editor/computed-columns/relation-column) Enforcing mandatory input items The use of visibility conditions and user specific booleans to control user flow There is nothing particula… - Have a number entry to force the users to enter 13 digits. I think you can calculate a string’s length using Glide’s calculated column, so only when they do enter 13 digits will you allow them to submit. - Have 4 columns to slice the input into 4 parts, then finally add a template column to add those 4 parts plus the 3 spaces in (XXX XX XX XX). --- _[View the full topic](https://community.glideapps.com/t/predetermined-mask-for-fields/34995)._