Yes, you can definitely raise a matrix to a power in Microsoft Excel without using the mmult function repeatedly. Excel has a built-in function called "MMULT" that can be used to multiply matrices, but it can be quite tedious to use it repeatedly to raise a matrix to a power. Instead, you can use the "POWER" function in Excel to raise a matrix to a power.

Here are the steps to raise a matrix to a power in Excel:

1. Enter your matrix into a range of cells in Excel. For example, you could enter your 40x40 matrix into cells A1:AN.
2. Select a range of cells where you want the result to appear. For example, you could select cells AP1:BF.
3. In the first cell of the selected range (AP1 in this example), enter the formula
   Formula:

   "=POWER(A1:AN, n)" 

   , where "n" is the power you want to raise the matrix to. For example, if you want to raise the matrix to the power of 2, you would enter
   Formula:

   "=POWER(A1:AN, 2)" 

   .
4. Press "Enter" to calculate the result. The result will be a new matrix that is the original matrix raised to the specified power.
5. Copy the formula down to the rest of the cells in the selected range to calculate the result for the entire matrix.

That's it! Using the "POWER" function in Excel is a quick and easy way to raise a matrix to a power without having to use the mmult function repeatedly.