I use two methods:
Method One - Excel
I use Excel's 'CONCATENATE' function. I enter the commands and variables into columns. Then I use a formula with concatenate to build the full string for each custom command. You then have to highlight the resulting column and do a COPY -> PASTE SPECIAL -> VALUES. Once you have the commands, you can simply COPY -> PASTE into a console or telnet session. Be cautious though, as you have to be absolutely certain your commands are built correctly and that you know exactly what the outcome will be. Once you hit paste, there's no turning back. If you don't write the config and make a mistake, you can always reboot the switch (assuming there's the opportunity to do so). You may also want to limit the number of commands you send to the switch at once as you may overflow the buffer. If you need an example, give me some sample data and I can send you a spreadsheet with what I'm talking about already completed for you.
Method Two - Perl
I have written Perl scripts that will take in a CSV file and parse it to arrays. I then open a telnet session and run the commands I need to, inserting the variables from the CSV file as appropriate. I have also used Perl scripts to do some work in reverse, namely crawling a subnet or list of IP addresses to login to each Cisco device and output information like 'sh ver' and 'sh cdp neigh' to get a quick glance at the network physical and data link layers.
