There are many different XLS compatible formats. CSV or TAB delimited are two very easy ones to work with. The newer formats are complex, compressed XML archives.
CSV and TAB and the ilk are easy. Just use IMPORT DELIMITER.
Example using a semicolon (;) separated file (normally with extension.csv).
/* Fields in temp-table matches the columns of the .csv-file */
DEFINE TEMP-TABLE ttExample NO-UNDO
FIELD col1 AS CHARACTER
FIELD col2 AS INTEGER
FIELD col3 AS DATE.
INPUT FROM c:\temp\test.csv.
REPEAT:
CREATE ttExample.
IMPORT DELIMITER ";" ttExample.
END.
INPUT CLOSE.
There are also some older formats like SYLK. There is an import for that hanging somewhere off the data dictionary tools if I recall.
Excel also deals well with HTML tables. A fragment of HTML consisting of tags is easily imported by Excel.
The newer .xlsx formats have no direct Progress 4GL import available and you would need to first research and specify the details of the format you are using. First you will need to uncompress. Then you need to handle the XML inside.