I am using 4MHZ, 16F877a, Timer1, setting TMR1H = $00 and TMR1L = $00. Tried to activate the timer as free running timer. Previously used to capture the timer time from 0 - 65536 microseconds (full range). Now that I am trying to extend the timer range and to respond to 1ms interval, I change the TMR1H = $FC and TMR1L = $18, with the codes below to capture the timer1 overflow.

Looping:
While PIR1.0=0
Wend
PIR1.0=0
TimerOverflow=TimerOverflow+1
LCDOUT $FE,$C0,DEC5 TimerOverFlow
If ButStop = 1 Then goto StopTimer
Goto Looping

But I am unable to get in 1ms interval. Can anyone guide me on this?