Write xpto1','xpto2 without the first and last quote because that the system puts in for you. In you where clause you'll use the IN operator

already try that...
but when i hit tab to next field it loses the values after the comma, it leaves me only the value before the comma

What is the data type of that criteria?

change the data Type to A and  it works (it is still limited to the number of chars), but it crashes my query now because of the other conditions.

Because it isn't a mandatory field i was controling it like this:

The number of chars is a more complicated issue. You will need to modify the deb and valdeb fields in the screen dictionary. You'll also need to set the data type of your parameter to a type that has defined a longer length for instance AVR, TRA...