Custom update in Transaction groups

Yes, I’ve defined a database driven provider but I want to use my table and I don’t want to INSERT but to UPDATE.
In the transaction group parameters there is an ‘Action’ tab and there is a ‘table action’ zone. There I choose update/select.
Here are 2 problems:

  • how to write the ‘where’ clause in order to update the right record in the table (I need an expression like this: WHERE tag_name={TagName}. Here {TagName} would be a function which returns the name of the current tag. Is there such a function? Can it be used in such way?
  • in the same transaction group, two items can’t update the same field, even if those items would update two different rows in the table;