OT: awk/sed: how to use a variable in an address range?

[O. Hartmann]

Hello.
This might be OT in FreeBSD list, but hopefully some of yours is 
involved in sophisticated AWK programming.

To keep a small shell script portable I use awk for separating an ASCII 
file from a home brewn scientific model software. The datasets of the 
output is enclosed by

/begin_data_set_##/
.
.
.
/end_data_set_##/

## is a two-digit counter, but not necessesaryly equidistant.

I would like to separate the file contaning all datasets via awk or sed 
into appropriate files - this is my intention, but I failed.

the simplest way - in theory and in my limitit ability of using sed or 
awk - is to print all lines between the (sed/awk) addresses

/begin_data_set_##/
...
/end_data_set_##/

but this does not work due to i cannot use variables in the address 
range specifiers neither in awk nor in sed like this:

awk -v nc=$NUMBER '/\/begin_data_set_nc\//,/\/end_data_set_nc\// { 
do-something-in-awk}' $input_file > $output_file_$NUMBER

nc in this example is set to the counter of the desired dataset.

I would like to use SED or AWK only due to portability reasons.

Any hints are appreciated.

Regards,

oh