Standard word processors, spreadsheets, databases and presentation software provide facilities to produce effective materials for in-house use. Excel was used for this development because it was readily available. Enhancements were made by adding short macro routines. Realisation of what is possible stimulates demand and the development of skills. More lengthy and versatile routines do require the development of programming skills.
Some teachers write textbooks.
Most, if not all, produce notes, exercises and other handout materials. Individual teachers can decide how far to develop their ILT materials production skills. The examples included with this article are listed below and can be downloaded from this website. They are Excel files and contain macros. The author would be very interested to receive feedback from any one who tries them.