PMDC SERVO MOTOR WITH quadrature encoder DRIVE ?

[phoenix_1]

Now I am probe on many ways to do next but I cant to image how.
1. I was setup count for QEI with friends from these forum to count from 0 - 12500 - becous my motor have gear 6.25:1 and 6.25*2000 = 12500(reding of one turn of motor shaft with 500 lines encoder) give me full 360' of output shaft range.That work extra.
Next : If I want to move for example 1mm on my mechanic I need one turn of output shaft that give me easi to control position of count from CW 0-12500 or CCW 12500 to 0.That is all in 16bit counter.
But what if I need to move more then 16bit counter ?
OK I can use PBPL and define 32bit variable - I was probe and it work 100%.
I can easy set to se if X VAR LONG number 25000000 that give me 25000000/12500 = 2000mm - inpresive!
But how I can my software variable defined as LONG from 0 - 25000000 to increment or decrement from hardware COUNT buffer wich count in circle from 0-12500 and vice verse ?
Is any idea becouse all what I was probe give me garbage of result.

Regards Robert