[Gretl-users] Runnining individual regressions in a panel

Dear Gretl-Community: Please apologize my ignorance, but I hope that someone can help me. I would like to classify a country as either one with some kind of a green revolution or not. I have a panel with some 200 countries and cereal yield for 40 years (1961-2000). What I have in mind is the following: I would like to run a simple regression for the period of, for example, 1960-1980, regressing cereal yield on an initial value of cereal yield and time. Then I would like to compare the time slope coefficient of this regression with the time slope coefficient of the same regression covering the period 1981-2000. If the slope coefficients of either both regressions are positive and significant or the time slope coefficient of at least the second regression is positive and significant, I would like to identify this country as one with a green revolution (which then serves as a dependent variable for subsequent analyses). I understand that I could run now some 400 regressions individually but I hope that there may be a faster way. Would anybody have an idea how I could program such a task in gretl? I appreciate your time and consideration. Thanks a lot, Marcus