Pass the on field value to another field of sales line

Hi Experts,

I have created the second line of item charges automatically while posting the item in sales order and I have freight charges field in sales line and this amount should be added to the second line of item charges of amount field

for example in first line of item I have freight charges =3000;

In second line of item charges I should have amount including VAT =3000;

how to achieve this?

please help me

You say you create the second line automatically during posting. I think that’s where you also update the amount field.