Method Community

I am trying to figure out how to make a formula field or calculate a value to place in field on screen.  For examples, I would like the portal user name to automatically create itself.  What I want to do is the first 5 letters of the last name, first letter of the first name and then followed by their account number.  For example: smithj10.

My thought is to collect the three field values, take the left 5 and 1 values of the first two and then concatenate the results of left(LastName,5) + left(FirstName,1) + AccountNumber.  Can you give me insight if this will be possible and the recommend onscreenLoad functions I should use to achieve this?

I found the answer.  I will run a character function and take the left 5 of the last name and save it as an action.  Then I will add another character function of the first of the first name and save it as an action.  Then another character function to join those two actions, and one last character function to join the joined actions plus the account no. on the screen.