The non-scripting solution:
First you need to build a summary table which is really easy to do. There are two options, use the tabulate and when your table looks like what you want then use save to table option. Or alternately from the Tables menu select Summary. Put your grouping variables into the group (so in your case Group and Time) then select the data column and then in the "Statistics" drop down menu in the summary dialog box select mean and then again select std dev. Before you hit the OK button check the little "keep dialog open" button so that if your table is not what you want it is easy to go back to the dialog and try again (and don't worry, we all do this multiple times to get exactly what we want).
Now you have a table with a Group Column, a Time Column, a mean, and a std dev. Now you can add another column (double click to the right of your last column) and now right click on that empty column and select formula. You want to build a formula that concatenates the mean, the ± symbol, and the standard deviation. The only trick is that the mean and std dev are numbers so I have a 3 part concatenate (look that up in the formula functions) with a char function to convert numbers to characters. I also use the ^ option on the character function to get a space for the "7" to control the length of the character. Maybe someone has a better solution to get a constant 2 digits when converting a number to a character.
Char( :Name( "Mean(Data)" ), 7 ) || "±" || Char( :Name( "Std Dev(Data)" ), 7 )
Finally to get the layout you were looking for you would Split your table. Table menu, Split option, dialog box: split by = group, split columns = new column, and group = time, again utilize that "keep dialog open" to go back and redo when you put the columns in the wrong places.
