How to get alerts when shipment xids reaches to final limit

Hi All,
I have a created BN rule for the shipment id as below.
{ nnnn:start=1000:end=4999}

That means shipment id starts from 1000 and goes upto 4999. After 4999 reaches, if we still plan the shipment, OTM fails that order release.

My requirement is, the moment only 100 count remains, i.e. once BN rule reaches 4900, then I should get a notification. I mean when BN rule reached certain limit, I should get some notifications.
Is it a possible scenario?

Please do add your comments if anyone has an Idea on this.

Thank you.
-Paddu