Try

FUNCTION TimeDiff_ut
LPARAMETERS tcStartTime, tcEndTime
LOCAL lnSec
lnSec = CTOT(tcEndTime) - CTOT(tcStartTime)
RETURN SUBSTR(TTOC(CTOT("00:00") + lnSec,3),12,5)

>
>a big big thank....
>There is still a little problem
>please try this code
>
>

>FUNCTION test91()
>
>WAIT WINDOW  TimeDiff_ut( "21:00" , "23:30")
>*-- return "02:29"
>ENDFUNC
>*-- 05/2005 UT Thread no 1011564
>FUNCTION TimeDiff_ut
>  LPARAMETERS tcStartTime, tcEndTime
>
>  LOCAL lnSec,;
>  cValue
>
>  lnSec = CTOT(tcEndTime) - CTOT(tcStartTime)
>  cValue = PADL(INT(lnSec/3600), 2, "0") + ":" + ;
>    PADL(INT((lnSec%3600)/60),2, "0") && + ":"
>
>  RETURN cValue
>
>ENDFUNC
>

>