Hello Mr. Fabio,
In addition to Eugene's answer.
Typically we encourage manually data entry to be done into PI Tags, this allows you to use the best of all our products, and if the day come where you have a sensor you can feed the same tag with the sensor data later in time.
If the user has access to PI System Explorer and the Read Only checkbox is unchecked on the PI Point Data reference, you can write into the PI Tag directly from the value field in PSE:
We also have a product called PI Manual Logger that can serve this task too.
Hope this helps.