GL account associated to each supplier for new bill

GL account associated to each supplier for new bill

Hello I'm facing problem for all items of my bills that are not inventoried.
The need is each time I enter new bill and after I select supplier the GL account section is autopopulated with default GL account (that I would like to add in supplier settings)
It's the way that most of accounting sofware do.
The zoho support designed me a script, we create a custom field in supplier to put GL account, then the script says that for a bill take this field in supplier to put in the bill

However, this script is act only when we valid the entry, so we have to select any GL account, validate the entry and then script change the account.

It's working but not the easiest solution, because we need anyway to select a gl account before validate the entry, and then in some case on a supplier bill we may have time to time a different GL account, or two GL account in one entry, but the script in this case overwrite the datas

The really best would be that kind of script act when we select supplier so it could put immediately the default GL account, and that GL could be changed before validate the entry.

Anyone get a solution ? This is what it's done with SAGE 50, I would like the same way.
Thank you in advance if anyone has solution