I agree with Bob Calver above me - quantizing could be your friend here.

The Edit menu contains commands relating to editing (changing) a song. This menu has standard editing features such as cutting, pasting, quantizing, etc. The editing commands normally affect the marked (highlighted) area of all selected tracks.

The Quantize feature can be used on MIDI data only hence it should suit your needs, presuming you are using a MIDI keyboard. This command “rounds” the times of notes to the nearest user-specified time interval. This is very useful for correcting timing errors like you described. Both the start times and durations of MIDI notes can be quantized. The resolution setting will determine the degree to which the timing is rounded. For example, if you choose a resolution of a sixteenth note, the notes in the marked area will be rounded off to the nearest sixteenth note. You may choose any resolution setting anywhere from a whole note down to a 32nd note.


Cheers,
Deryk