Drop down list macro

I would like to create a macro whereby I could invoke a drop down list from which I could select a value from a list to be input in the current cell. The values for the list box would be stored in the worksheet in a matrix of cells, let's say for sake of argument in a 4x6 arrangement. The drop down list should take on the form of the matrix. Could someone please give me an example of such a macro.

Thanks.