I basically can only play with D fingering so need to change all my music so I play it with D fingering. If I play a C whistle with D fingering I move all the music up one note. I know this is right. But how many notes up do I go to play an A whistle? Bflat whistle. E flat Wh. and a G? I’m not worried about flats and sharps I can hear when I need to put them in. I hope this makes sense. I have to play this way as I have virtually no short term memory and can’t learn other fingering. The music given out in our group often needs to be changed for different whistles and I am getting stuck when I type it into the music software I have. 
i would not transpose anything at all in case you do live recordings. just use http://www.ronimusic.com/ and put it in D.
if you use sheet music, from C sharp to D is half a note down, form C to D is a whole note down etc…
but i don’t know any software that does this for sheet music, i’m sorry.
If you can make a midi file from your software, type in the notes as per the sheet music you have, then use Tabulature karaoke to:
i) change to D tab fingering from e.g. F - it’ll show the tab onscreen, and you can print the tab’ out. Or even convert the tab’ back to sheet music manually - time consuming but possible, 'cos I’ve done it meself.
ii) then use yer A (Bb, G, etc) whistle to do the transposing for you
i.e. use the D fingering on yer A whistle.
HTH if I haven’t misunderstood yer problem.
C whistle: transpose up 1 step.
Bb whistle: transpose up 2 steps.
A whistle: transpose up 2-1/2 steps.
Eb whistle: transpose down 1/2 step.
I.e., transpose up or down as many steps as the whistle is pitched lower or higher than D. Noteworthy Composer will transpose automatically, but it is fairly expensive software.
The (free) ABC program abc2abc can transpose abc notation. Now if only we could all learn ABC. 
This came up recently. Anyway I have a chart which does it for me at
http://www.maths.warwick.ac.uk/~bjs/key-change.jpg
The left hand side shows the key as written on your music sheet. The top shows the key of the whistle you are about to play. Read off from the table the key that will emerge when you play pretending that you had picked up a D as usual.
Brian
abctools does a nice job of transposing and it’s free
http://www.magma.ca/~scarlett/abc/
Mozart works well to transpose sheet music, but it’s expensive. The viewer is free but the full program is needed to do transposing. You can download an “evaluation copy” for 30 days. It allows you to do a wide range of things to a score in addition to transposing.
Finale Notepad
Put that phrase in google, and you will come up with the website really fast.
It is a “shareware” or trial version, but it does not expire, and never asks you to register. It allows most things, and is the most powerful free sheet music thing I have seen. The only things I have found that it wont do are: changing time signature in the middle of a song (for instance from 4/4 to 3/4) and changing key signature in the middle of a song (from say D to C)
IT WILL TRANSPOSE though, so simply choose your key, type in the song exactly like it appears wherever you have it (actually point and click it in) and then change the key to whistle D.
Nico
Thanks all. I think Ridseards’ explanation is the answer I needed. I’m not sure about the half step in the Sibelius demo I’m using. So if I’ve got it right the G whistle would be four notes up?
BJS. I saw that chart. btw I lived in the bungalow next to Canley Halt Railway station and often popped down to Warwick Uni for concerts and stuff before moving to work firstly in Nuneaton then in Scotland. Because I’m dyslexic due to Chronic fatigue Syndrome I’m having problems working from the chart. 
Yes, basically it would be four notes up (what’s called a perfect fifth). If you’re counting the steps:
G to A is one step.
A to B is one step.
B to C is one-half step.
C to D is one step.
The total is 3 and 1/2 steps up. (A half step is a semitone, a whole step is two semitones.)