After changing the datas in related records , how can I automatically refresh the below merge field (summary field) ?
You could replace the summary field with a calculation field in the parent record that uses sum() to compute the same value.
you can commit records after every edit of data in the portal row. This causes the portal row to lose focus, however, and this means that additional scripting may be needed to put the focus where you need it.
Retrieving data ...