How to create ExtraField

Developing for Dolibarr
1

Hello

I need to add the number of days field on the service part of “invoice / quote / order” when creating
Currently I have managed to add the number of days field but I can’t find how to change the calculation formula to have the (Unit price x number of days x Quantity = total HT), thus recovering the value entered to calculate the sum, then displaying the number of days field in the PDF.

So my questions are as follows:

1/ Recover the value entered.

2/ Modify the calculation.

3/ Display the new field in the generated PDF format.

Thank you.

2

Your question is not very easy to understand:

When creating an extrafield i.e. in products:
/product/admin/product_extrafields.php?action=edit

and you want to calculated fields from other fields I have setup an extra field like this:

ksnip_20250111-103325
ksnip_20250111-103325923×650 13.5 KB

hope this is what you are looking for.