Update Existing Rows in Destination Table Using Source Webhook Data

Consider the following setup, I have two tables - destination table and source table. Source table receives webhook data. Destination table has various columns and rows, out of which one column is named ‘webhook data’ and one column is index column which has unique values. Now when i receive data in source table from webhook, i want to populate the particular row of webhook column of the destination table that is, particular cell. There is functionality for writing to table but it only inserts rows, not update particular cells of existing rows. Look up works by pulling data from other table. I want push functionality from one table to another to existing row/column. Is there a way to do this?