How to call the function in pricing formula

Hi team,

I have created one new custom funtion in order to get the latest Item layer cost. Then I need to add 10% to that Item layer cost. For that Iam creating one formula with the 2 steps

Step 1 -- trying to get layer cost using newly created custom function

Step 2 -- .1

my formula will (1*2)+1

I am not able to call the function in pricing formula screen.

please help on this.

Regards

N.Senthil