Extracting random place data

Hi I have a little long question. I have California area longitude X(-119.86, -116.57;),latitude Y(35.89, 38.70;) and Magnitude(see attached excel file) . I need to choose 45 random small the same size square boxes in the area. All small square boxes width(length)=0.18. If there is no magnitudes in any of small boxes, random should choose another square automatically. These means all 45 small boxes must have magnitudes. Than it needs plots Maximum Magnitudes(x) to Log(Cumulative number)(Y). My Cumulative number is sum of Maximum magnitudes in the small boxes. Small boxes would have different amount of magnitudes, such as first box 5 magnitudes(2.5, 3.1, 4.2 2.6 1.9), 2-box 7 magnitudes and so on. 1-box maximum magnitude will be 4.2. In the way we should get 45 Maximum magnitudes. Notice Log(Cumulative Number) should be in decreasing style length(Mmaxs):-1:1.(Please have a look example jpg plot) So I should do the plots 100 times(100 curve in one graph). Also finally average of the 100 curve also needed.

Thanks so much!