Lpc2000

Hi everyone,
I'm searching for solve a big problem in one of my projects.
We use FreeRTOS in LPC ARM microcontroller and scheduler is called 
by a tick made with Timer0 Compare0.
Unfortunately, Timer0 is configured, by FreeRTOS sources, as reset 
on match Compare0.
Our board has a capture pin on P0.22 (CAP0.0) used to detect level 
duration and we have not to reset Timer0. So we configured Timer0 as 
continuously running and, on Timer0 Match0 interrupt, we reloaded 
new match value on register permitting us to have a periodic tick of 
100 microseconds.
To set the new match value I use following code:

T0MR0 += L_COMPAREMATCH;

where L_COMPAREMATCH is equal to 6000. Doing so, our next tick is
after 71 seconds (that is about 0xFFFFFFFF clock at 60MHz)
If I substitute previous code with:

T0MR0 = T0TC + L_COMPAREMATCH;

our next tick is about after 100 microseconds.
But I cannot use this code, as I will lost tick between match on 
T0MR0-T0TC and recalculation-setting of next compare.

How can I do? I cannot use Timer1 for O.S. tick as it is used for 
other purposes...
Is it possible that between match on Compare0 and write of next 
Compare0, T0TC counts as many ticks as my match value? I tried to 
increment tick value of compare, but nothing, it doesn't work! My 
LPC works at 60MHz as Timer0, so I don't think that it executes about
20 instructions (corresponding to flag check and T0MR0 += 
L_COMPAREMATCH;) in 100 microseconds!!!!

Thank you for your attention
Enrico D.M.
Vicenza - Italy