How are you writing your data to Excel 2007 -- PROC EXPORT?? The Excel LIBNAME engine?? Or, are you using ODS methods??
If you are using "export" methods like PROC EXPORT, the LIBNAME engine or using ODS CSV, then you do not have a way to alter the font when Excel opens the data.
However, if you were using other ODS methods, such as ODS MSOFFICE2K, ODS MSOFFICE2K_X, ODS TAGSETS.TABLEEDITOR, ODS HTML or ODS TAGSETS.EXCELXP, then you could change the font of your procedure output (such as PROC PRINT, PROC REPORT, PROC FREQ, etc) using either a STYLE template or STYLE= overrides (for PRINT, REPORT and TABULATE).
How you are creating files for Excel will determine whether you can do what you want.
Thank you Cynthia. I use the libname method, which seems to be the only way mentioned for accessing Excel in SAS base programming 1 and 2 training. This week I attended PugSUG meeting where Vince gave a talk about SAS and Excel. He also gave us some great examples. I will give the ODS approach a try.