Gouds No worries - the forum is for all questions R3, no matter how deep. We cannot guarantee that we can react quickly as paying customers must come first. But as long as you can wait in these cases, there is no reason not to ask 🙂. Plus, there are other community members that might know the answer.
To your question: Yes, you can lookup any other record inside your backend function (via a SELECT statement, with the record ID). But to do that, this record has to exist first. So you cannot click on a button to create a record in table2 and lookup stuff from table1, if the record in table1 has not been created yet (e. g. form was not saved yet).
If your primary record (table1) exists (form has been saved), you can send its ID to the backend function when clicking on the button. To get the record ID of the current form, you can use app.get_record_id(0) inside your frontend function. When you send the record ID of table1 to your backend function to create the record in table2, you can use it to SELECT any value that exists on table1.
Alternatively, if you just want to calculate a split value from something on table1, and the corresponding input field from table1 is also on your form, you can just read the value from this field and also send it to your backend function. Then you do not have to do any SELECTs and just work with the values you have collected from the form.
