>if thisform.text1.value=14:35 then thisform.totaltxt.value=14:35
In VALID event of the TextBox:

** Valid EVENT of the Thisform.Text1 
LOCAL ret_val

ret_val =  VAL(LEFT(this.Value,2))     < 24 .AND.;
           VAL(SUBSTR(this.Value,4,2)) < 60 .AND.;
           VAL(RIGHT(this.Value,2))    < 60
IF ret_val
   thisform.TotalTxt.Value = thisform.TimeAdd(this.Value, thisform.TotalTxt.Value)
ENDIF

RETURN ret_val