So if you can wrap the point data from your DEM into a simple for loop (lat/long/elev) you should then be able to output a file (after some judicious data choices) with daily, monthly or annual insolation for each point in the DEM, although this would obviously be affected by things like weather, but there's daily models for that as well, or at the very least, weather station data.
To wrap an R script in matlab you just use the call: