INSERT multiple raw with 1 form

[Fortunato]

I have a form for tracking expenses. In this form, user can select if the transaction is a income, expense or Bank Transfer. 
if is expense, form shows only account, amount etc… 

if is income, form shows only accont, amount etc

if is bank transfer, form shows account income, account expense and amount. 
I need an automation that insert 2 row, one for debit movement and one for credit movem te whith same amount. 
how is it possible?