There are several ways that you could approach this, depending on your data types and value requirements. One big question is, can your exponent be fractional, or is it limited to integer values? You could build a Stateflow chart or write a MATLAB Function block, if using Simulink. You could also build a subsystem that will repeatedly multiply by your value, using only basic blocks.
If generating HDL Code from MATLAB, you can write your own function, using whatever technique you wish.
