How to add validation on save document based on value fetched from database

[Alaa_Badri]

Dear @tmatteson
Did you have any help on this topic i creaded about this issue

Overlap validation

i’m using below code for avoiding overlapping for a custom field called facilitator in Event document so I need to check facilitator name against date so if he has another document saved in the same event start and end time not able to save the document but the code not working properly frappe.ui.form.on("Event", "validate", function(frm) { frappe.call({ method: "frappe.client.get_value", args: { doctype: "Event", fieldname: "…