Custom block with OPC read/write blocks - passing a parameter

Suppose I have a custom block I use mask to pass a paramter foo.Inside a block I have several opc read/write blocks.I want that blocks will recieve a parameter in cetain template that I decide in advance as Item ID for example.

Let suppose I have number of opc read blocks in my costum block

//Project_name/***.boo1
//Project_name/***.boo2
//Project_name/***.goo3

and etc.

Instead of asterics I want that it will be foo so I will get:

//Project_name/foo.boo1
//Project_name/foo.boo2
//Project_name/foo.goo3