Sounds like you need a combination of reading filenames, and generating filenames:
A = dir('D:\mydatahere\Wow*.mat');
A is a structure containing the filename of every mat file, starting with Wow, in that folder. Assuming that there is only one:
wowfile = ['D:\mydatahere\' A.name] %will put the name of that file into wowfile. Read wowfile by the appropriate means.
A_filename = ['A' num2str(an_A_file_to_read) '.mat'];
Change .mat to whatever extension you need.
