Hi,
Yes, we can define the values directly within InfoPath and there is no limit on the number of entries the list box can have
To define values direct within InfoPath, steps to follow
1. Open the list box properties
2. Under list box entries, select Enter list box entries manually
3. Add the values to be displayed in the list box and close the properties window
Hope this helps you!
Shilpa
INFOPATHDEV India