Multipunching questions

The client is expecting code in the data file must be the same as in the questionnaire.

For example:

A question like, Product you bought:

1- Product A

2- Product B

3- Product C…

If an interviewee said: 2 and 3, it will be punched like “[space]23” or “23[space]” and not binary form “011”. How can we achieve this.