Need help in Transation table coding

Question

Hi all,
I need help in how to transfer data from one account no to another account no in single table.
In
this customer will get his account no from dropdown list(it will come
automitically thru his session) and customer has to write the
destination account no in textbox and the amount he is transferring
will be written in another textbox.Before transferring the amount,
destination account no and the balance amount should be validated.

Customer_Account table:
AccountId UserId Status Balance AccountCode
101            xyz      A        2000     SB ->Savings
102            abc      A        3000     SV->Current
103            yxz      A         4000    SI->Joint

For SB MinBalance 500,SV 1000,SI 2000 should have

Transaction Table:
TransactionID, AccountID, TransactionType, Amount, DOT, UserID ,SourceOrDestAccountId ,TransferFlag,Balance

In this If AccountId 101 want to transfer his 1000 amount to AccountId 102 
AccountId 101 will be debited and AccountId 102 will be credited.

Please somebody help me in coding, this problem.

Thanks,
Masum