Get a specific value when date = another date

[Badzreyes00]

Hi Everyone, Good day! I hope you can help me with my problem here.
I have 3 tables:
T_ACCOUNT - Contains all the account information
T_BILL - This is the transactional table of T_ACCOUNT so if an account in T_ACCOUNT does not have any transaction yet, it won't be in this table
T_APPL - Have all the information of product applicants

Now if we want to know the current balance of an account in T_ACCOUNT we will compute it in T_BILL using IF(SUM(debcred='D',trxn_amt*-1,trxn_amt)) and it is using trxn_date for its date.
T_APPL is using appl_date

Now I want to know the balance of an account on the date of his application in T_APPL or What is the Balance of an account when T_APPL.appl_date=T_BILL.trxn_date

So far I managed to join T_APPL and T_ACCOUNT, and I can join T_BILL into T_ACCOUNT and create a column for it's balance. So what is left is to ADD a NEW COLUMN in T_ACCOUNT that contains a stagnant value for "Balance at the time of application"
I hope I explains it well and I hope that you can help me, thank you so much in advance!

Maybe I'm just complicating it into my head but I hope you can help me. Thanks again!