Is this what it looks like in the database, just a time field with no date?
And how do you want to display 23:45 + 22:45? Should it have an additional days column, or show 56:30?
You can accumulate the times using a formula in the details (or wherever) using a formula such as:
whileprintingrecords;
numbervar Hours := Hours+val(left("01:45",instr("01:45",":"

-1));
numbervar Minutes := Minutes + val( mid("01:45",instr("01:45",":"

+1,2));
If this is within a group, then first set the values to 0 in the group header:
whileprintingrecords;
numbervar Hours := 0;
numbervar Minutes := 0;
Then in the Group Header (or report footer if there isn't a group) use the following in a formula to display it:
whileprintingrecords;
numbervar Hours;
numbervar Minutes;
Minutes := remainder(Minutes,60);
Hours := Hours + truncate(remainder(Minutes,60));
totext(Hours,0,""

+":"+totext(minutes,0,""
-k