VBA to: Look in folder for .xlsm file, and list its filename in cell

Hi,
I'm looking for VBA code that will look in a specific folder (fixed filepath) for a .xlsm file (there will only be one .xlsm file in the folder). I would then like to have the filename of that single .xlsm file displayed in cell A1.

How do I write a macro to:

Look in:
C:\Test\Test_Folder
Find:
".xlsm" (unknown filename)
Range("A1"). Value= (unknown filename)

Thanks for the help!!!