Measure the time elapsed between two successive rising edges of a pulse signal

Hi, sorry, not much help, I don't want to waste your time, but this is a suggestion just to think of a way of on-circuit time measurement with the devices you are using.
I made a CD4026 pulse high time and low time timer with analog devices, using a 4060 to get a 10KHz clock (far, far too slow for what you're doing, I think) as I want to see how accurate or inaccurate a 0.125 seconds high and 0.125 seconds low astable timer is working so I can co-ordinate it with two other astables on a "clockwork toy" style motor circuit.
My solution is really basic, not great to say the least, but it works for my needs: The measured signal goes into a "slave" 555 trigger pin via an NFET and a PFET sends the same signal to the reset pin. When the high/logic 1 signal ends, the "slave" (monostable) timer triggers a second monostable 555, which clock inhibits the first CD4026 in the counting/timing chain, and this way the time is stored on the 7-segment displays for a few seconds or more (adjustable hold using trimpots), when the hold function SE555 pulse ends, it triggers a third monstable 555 which sends a blip pulse to the reset pins of the CD4026s, and then the whole counting/timing sequence starts again. To count low time, the trigger and reset signal cables are reversed on the "slave" 555. Obviously, I need two circuits to achieve this, it's a really inefficient circuit and it could be far better in many ways, but it works enough for a hobby tool.
I hope you get some good ideas from my caveman solution to a far simpler problem. Wishing you success with the elapsed time timer and regards.