Hi,
The polyfit and polyval functions may be able to help you out in this regard. Here is an example of how you can use it for interpolation:
X = [1:10];
Y = [1:10];
c = polyfit(X,Y,1);
Input = [10:0.1:11];
Output = polyval(c,Input);
disp(Output);
Your latitudes and longitudes from your dataset can be used in place of X and Y and your Input would be [40.5:0.1:43.5] in your case. Do take a look at the documentation of polyfit and polyval for more examples