Ok, simple enough.
In Mathcad, just go to Insert>Component... and select "File Read or Write" in the dialog box.
Then, make sure the "Read from a file" radio button is highlighted on the next screen.
Under the next screen, select "Excel" from the File Type drop-down, choose your saved Excel file with the Browse... button.
Click Ok and Mathcad inserts a File Read component into your worksheet. See how the component is on the right side of the := assigment operator? Now all you do is tell Mathcad what variable to place the data from your Excel sheet into. Just for simplicity, type in "A" into the variable placeholder. If the component turns red with an error you should go back and make sure that the file you specified actually exists.
Then type "A=" to dump what is in A to the screen. You should see all of the data from your Excel file in the A matrix!
From there, you can access the data in A just like you would any other matrix.
For example, if you want to store only the 3rd column to B, you'd type:
B:A(Ctrl-6)2
(2 is the column number, because the columns are numbered 0,1,2, etc.) Ctrl-6 makes a Matrix Column operator and can also be found in the Matrix toolbar
If you want to store only the 3rd row to C, you'd type:
C:A(Ctrl-1)(Ctrl-6)2
Ctrl-1 is the Matrix transpose operator flips the matrix along its diagonal so all the rows become columns and all the columns become rows. It shows up as a superscript T. The the Matrix Column extracts off the 3rd column (formerly the 3rd row befor the transpose) and puts it in C.
If you just want a single number from A, just type:
A[r,c=
Where r and c are the row and column indeces of the number you want.
Now, lets say that you have a formula f(x,y) and your A matrix contains two columns corresponding of values of x and y, and you want to evaluate this function for all of values of x and y in your Excel sheet.
Make a range variable that starts at 0 and goes until how many rows you have. Remember that the value of the index is always one less since it starts at 0.
i:0,1;rows(A)-1
As our test function let's find the distance of an (x,y) pair to the origin.
f(x,y):\x^2 +y^2
(Translation: f(x,y)=sqrt(x^2+y^2)
We'll make a column vector called d which contains the distance of each (x,y) pair
x:A(Ctrl-6)0
y:A(Ctrl-6)1
d[i:f(x[i,y[i)
And there you go! First we extracted the columns of A into x and y, and then we used the subscript operator with a range variable to store the results of the function. Type "d=" to see the answers.
Hope this has helps!
-Matt