how to use trigger when specified table column update in mysql

Hi all,

I have a 3 table  explained in below

 

table1 contains below columns 

 

id	Currency Symbol	Currency Name
1	$	dollor

 

Table 2 contains below columns

id	Project	CurrencyId
1	Project#1	1

 

Table 3 contains below columns

id	Item details	projectId	Currencyid
1	CPU	1	1

 

table 1 refers currency master 

Table 2 refers project details

table 3 refers Item related for projects

i need to write a trigger when project table currency id changes(update) that reflects Item related for project table 

 

Example:

If project table currency ID updates to 2 at that time trigger need to be generated and update the Itemrelated projects table currency id column