Help

I'm trying to fill in a job application with very small boxes and I need a word to summarise the times I went on tightly focused day training courses.

Sometimes 3 or 4 a year, sometimes only one, so not regularly. Frequent doesn't feel right nor occasionally.

I want to say passim, but that's really only for texts. It has exactly the right nuance if only it wasn't the wrong word.

And I can't fit intermittnetly in.

edit And apparently can't spell it either.