So I have an app called Bill Entry where I have a lookup field called Customer and a lookup field called Utility Account.  The lookup field "Customer" relates to the field Account_Name in an app called Accounts.  The lookup field "Utility Account" relates to the field Acct_Num in an app called Utility Info.  So, in the Bill Entry app, I am hoping that when I select the Customer in the drop down field that only the Acct_Num related to that Account_Name will show.

I am just beginning to use this app and there is very little data in it but before long as it is currently set up I will have to chose from hundreds of utility account numbers whereas I am sure there is a way to only show the ones relative to the selected Customer.  Likewise, I am aware that I can "search" this field but often times account numbers are 12 numbers long and the first seven numbers might be the same for say a hundred records so this will not work. Any help anyone can offer is appreciated.    

Cheers!