The oldest version I've is VFP8 and I get correct result under it. Here's my test code( 2 vesrsions)

CREATE CURSOR test (tim c(8))
INSERT INTO test VALUES("10:30:15")
INSERT INTO test VALUES("12:30:15")
INSERT INTO test VALUES("18:00:10")
INSERT INTO test VALUES("10:10:30")

SUM CTOT(tim) - CTOT("00:00:00") to lnSec
? PADL(INT(lnSec/3600), 2, "0") + ":" + ;
				PADL(INT((lnSec%3600)/60),2, "0") + ":" + ;
				PADL(lnSec % 60,2, "0")

SUM VAL(LEFT(tim,2))*3600 + ;
	VAL(SUBSTR(tim,4,2))*60 + ;
	VAL(RIGHT(tim,2)) TO lnSec

? PADL(INT(lnSec/3600), 2, "0") + ":" + ;
				PADL(INT((lnSec%3600)/60),2, "0") + ":" + ;
				PADL(lnSec % 60,2, "0")

>thank you for reply,
>i try as under,but i get error result .the result is 15
>but the data at myfield as under
>rec1. tim= 10:30:15
>rec2 = 12:30:15
>rec3 = 18:00:10
>rec4 = 10:10:30
>
>i need the result as 51:11:10