Query: Periphrastic Future

[Colin Harrison]

Does anyone out there know of any languages that form a periphrastic future
tense using the verb "do" (or "make") as an auxiliary (i.e. something like
"He is DOING to write" meaning "He is going to write").

I have a future tense formation in a Papuan language that seems to be doing
this (although it's not entirely clear) and I'm wondering if there's a
precedent.

Thanks!