[Gretl-users] cdf intervals

Dears My problem is the following. I have data on income in both values and income intervals. Using a log likelihood for both sub samples, I want to get parameters of the joint sample. My problem is how to define the income intervals in Gretl, and apply them to a cumulative density function, normally distributed ( not standard cdf). I want to express the income intervals as a difference between cumulative density functions at each point. Any idea how to do that?? Hope I’m clear. It is clear that I’m a beginner in Gratl. Thanks in advance Rezi