display image file from concatenated filename

I have images with sequential numbers in their JPEG filenames - eg pic-06.jpg
I want to display a random image by generating a random number which is then concatenated with text to create a suitable filename - eg pic-23.jpg.

I can do the above but I do not know how to get Excel to use the concatenated filename to load and display the appropriate image (if it is indeed possible to do so)

Any suggestions?