Is it possible to transform an SAP error message into a popup?

This is possible, e.g. with:

V[_message] and V[_msgno=440] and V[_msgid=EU]

   Message "&V[_message]" Title="Attention please..."


where you replace  "440" and "EU" with the message number and id of your message.

In order to get the message number and message id for a certain message, you can use F1 on the message line.