How can I grep data in Excel?

Still no decent answers? Since you said grep, I assume you know how to use a shell;

$ link=http://wizard.ae.krakow.pl/~jb/xls2txt/xls2txt-0.13.tar.gz
$ wget -nv "$link" && \
  tar xf `basename "$link"` && \
  cd $(basename "$link" .tar.gz) &&\
   make
2013-07-24 URL:(...)/xls2txt-0.13.tar.gz [12419/12419] -> "xls2txt-0.13.tar.gz"
cc -O2 -g -DVERSION=0.13 -c xls2txt.c -o xls2txt.o
cc -O2 -g   -c -o ole.o ole.c
cc -O2 -g   -c -o cp.o cp.c
cc -O2 -g   -c -o ummap.o ummap.c
cc -O2 -g   -c -o ieee754.o ieee754.c
cc -lm  xls2txt.o ole.o cp.o ummap.o ieee754.o   -o xls2txt

$ awkf() { awk -F\\t '{ printf "%20s | %-20s\n", $1, $2 }' ; }
$ x2t() { ./xls2txt $1 C4:D5 | awkf > `basename "$1" .xls`.txt ; }
$ x2t ramesh2.xls ; x2t ramesh.xls

And the report:

$ grep MXS1268 ramesh*txt
ramesh.txt:         Operator ID | MXS1268
ramesh2.txt:         Operator ID | MXS1268

On Linux or Cygwin:

$ xlsx2csv myfile.xlsx | grep MXS1268