vb:if post matches regexp. Possible? How to?

[Zillo]

Hello,

I want a content to appear after each message (near Edit Reply etc.) if a user uses an specifc tag. I wonder if there is some way this can be done with vb:if. For example vb:if tag or a vb:if where the post matches regexp (do not know if anyone of them are possible).

Do you know what vb:if condition can be used?

Thanks in advance