This version uses the windows COMPUTERNAME environment variable. I don't know if that would be server name. Open a command prompt and type "SET" to see all the env variables. There should be one that is server name.
Then use SYSGET to retrieve the value in SAS.
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data _null_;
today=today();
server = sysget('COMPUTERNAME');
length path $256 fileref $8;
do i = 19 to 1 by -1;
prev = intnx('MONTH',today,-i);
path = cats('\\',server,'\f\report store\sasdata\four_',put(prev,mmyyn4.),'.TXT');
fileref = cats('ACN1F',put(i,z2.));
put 'NOTE: ' fileref path;
rc = filename(fileref,path);
end;
run;
filename _all_ list;
[pre]