Anonyms ,
I would try the following below. Let me know if this is what you wanted.
%Select Excel File to Load
[filename folder] = uigetfile('*.xls*');
%Read sheet 1
sheet = 1;
Data1 = readtable([folder,filename],'Sheet',sheet);
Data1 = table2array(Data1);
%Read sheet 2
sheet = 2;
Data2 = readtable([folder,filename],'Sheet',sheet);
Data2 = table2array(Data2);
%Read x, y, and z
x = Data1(2:end,1);
y = Data1(1,2:end);
z1 = Data1(2:end,2:end);
z2 = Data2(2:end,2:end);
%Calculate Average
zavg = (z1+z2)/2;
%Generate Surf Plot
[xg, yg] = meshgrid(x,y);
surf(xg',yg',zavg)
