Trigger + CONSTRAINT ???

I have 2 tables

Primary_Table (Key, ........)

Foreign_Table (Key_1, Key_2, ............)

I want this:

If I update the Key in Primary_Table then
Key_1 is Update where Key_1 = Key

AND

If I update the Key in Primary_Table then
Key_2 is Update where Key_2 = Key

I can not use CONSTRAINT because I can not use ON UPDATE CASCADE for this case (It not possible to use 2 CONSTRAINT WITH ON UPDATE CASCADE).

I WANT TO USE TRIGGERS

This is my trigger (but I am not sure it is the best way ?)

CREATE TRIGGER Test ON [Primary_table]
FOR UPDATE
AS

Declare @NewValue varchar(30)
Declare @OldValue varchar(30)

SET @NewValue = (Select Key From Inserted)
SET @OldValue = (Select Key From Deleted)

UPDATE [Foreign_Table]
SET [Foreign_Table].[Key_1] = @NewValue
FROM [Foreign_Table] WHERE [Key_1] = @OldValue

UPDATE [Foreign_Table]
SET [Foreign_Table].[Key_2] = @NewValue
FROM [Foreign_Table] WHERE [Key_2] = @OldValue


Sorry for my english.
Please consider I am a beginner