Increment ID in invoice/contract

[eymen-elkum]

Hello,

Add new int field to the parent entity and set the value using this formula script:

$invoiceCount = record\count('Contract', 'contractId', contractId);

ifThen(entity\isNew(), $invoiceCount = $invoiceCount + 1);

record\update(
    'Contract', contractId,
    invoiceCount, $invoiceCount,
);

[timarebel]

Hello

I want to make an ID number where which contract has invoices and this invoices have ID incemented by 1
how can I know the previous of each record invoice which below to that one contract.