Complex expression in Depends On in Customize Form

Frappe Framework Customization
1

I have ( link feild to currency called ‘currency_field’ ) and ( another field witch is float called ‘exchange_rate_field’ ), now I want ( when the user select not the default currency of company => the ‘exchange_rate_field’ will be showed, so for that I wrote this expression
eval:doc.currency_field != Company:company:default_currency
in ‘Depends On’ in ‘Customize Form’ on the ‘exchange_rate_field’ Editing Row.
but I faced problem which is Invalid “depends_on” expression

Is there another expression to do it, or another way, or another solution!?
thank you in advance

2

After many attempts, the solution is

 validate: function(frm) {
		frm.trigger("calculate_final")
	},
	test_amount_other2: function(frm) {
		frm.trigger("calculate_final")
	},
	exchange_rate3: function(frm) {
		frm.trigger("calculate_final")
	},
	calculate_final: function(frm) {
		if (frm.doc.exchange_rate3 && frm.doc.test_amount_other2){ 
			var final = flt(frm.doc.exchange_rate3 / frm.doc.test_amount_other2);
			frm.set_value('test_amount_default', final);
		}
	}