Running Macro On all Files In Folder

I have a macro that i originally created within an excel spreadsheet.
I would like to store it within the personal macro workbook in visual
basic editor so that i can run it on multiple files.

What I am hoping is for someone to help me write something so that i
can run the macro on all files within a folder on my desktop. I am
having trouble with the code, since im quite the novice.

So i would need the macro to open a file within the specified folder,
then run the macro that i have written, and save the file within
another folder on the desktop.

So i need help with the running on all files in a folder and also
saving the file as. I am having trouble making this macro because it
isn't referring to a specific file. Any help would be very very much
appreciated!!! Thank you!!