Rewrite cookie then force cache refresh?

[StewardManscat]

We show empty frames instead of pictures until a user pays. Once they pay, their access level goes up. The access level is in a cookie. We rewrite the cookie ok.

But pages do not show pictures until either the user hits refresh/reload, or they shut down their browser and restart.

Ouch! Enormous support issues.

We looked at the Cache-control headers and could not spot one that might do what we want.

Normally caching is good.

Is there any way we can say "as of now, everything in your cache from our site is outdated" ?

Many thanks.

[mystrymaster]

I think you can set an expiration date in the headers

[StewardManscat]

Thank you for the suggestion.

To clarify: the "expiration date" is user-driven. I want all pages to expire "at my command" (when the user has paid).

The cookie already has a time-limit, and most support issues are avoided by not replying: the poor customer tries it a couple of hours later and it works.

Looking for a way for the server to invalidate the cache at will....