calendar-insert-at-column

calendar-insert-at-column is a compiled Lisp function in `calendar.el'.

(calendar-insert-at-column INDENT STRING TRUNCATE)

Move to column INDENT, adding spaces as needed.
Inserts STRING so that it ends at INDENT. STRING is either a
literal string, or a sexp to evaluate to return such. Truncates
STRING to length TRUNCATE, and ensures a trailing space.