Basic System Diagram

INPUT Any Input that provides a single event and one clock signal

PROCESSOR 1 Pair of 4510/4511 Counting up one for each input event   OUTPUT 1 Pair of Number Displays     PROCESSOR 2 Digital Logic Checks to see if the Binary Word  is 00000000       OUTPUT 2 An Event that You Set Up It is triggered by a Lo

Using two 4510/4511 counting sets joined together, you can count from 0 to 99.  Here's how to trigger your secondary output begin when the number changes from 99 to 00.

The Binary Word at 99 would look like this.

One more clock signal to the 4510 (holding the ones place) would change the Binary Word to this:
 

A Digital Logic System recognizing a number is very simiple.

You place the Binary Word Output from the 4510 to a set of  Logic Gates.

For example, if you want the system to recognize the Binary Word of [0000 0000] use several OR Gates this way.

This [00 00 00 00]  is the only set of inputs that will provide a Lo output at Gate 7.
You can use that change of state at the output to trigger any number of events.