Modifying Lineitems data

We are on Unifier 24.8 and have a use case question as below:

While creating a new line item, when we enter data in an integer field, the data on same field on all the other existing line items are altered in a sequnecial way based on this entry.

So, if we have BP with lineitems with a field having sequence no as 1,2,3,4,5…. and if I enter a line item with sequence no as 4, the data on the exiting line item with data as 4 becomes 5 and so on.

If we cannot do it in Unifier directly, can it be done with web services or other integrations.?