Find all possible combinations of letters

I have 8 letters in A1:A8
a,b,c,d,e,f,g,h

I want to make a macro to find all possible series of 8
letters, in which all the letters are used.

Also the series should not have more than two
alphabetically consecutive letter following eachother.

E.g a,b,c, or c,b,a is not allowed, but a,b,d and a,c,b is allowed.

Thanks for pointing me in the right direction, however i probably
didn't make it very clear what i wanted to achieve in the first post.

I want to generate the whole series of 8 characters, not just the first 3,
and nowhere in the series should there be more than 2 alphabetically consecutive characters following eachother.

I.e: a-b-d-e-g-h-c-f

hi.. i want to find all the possible combinations of 8 characters including letters and numbers.
The letters should be all capitalized and the combination should be letters and numbers alternately.
This are the examples:
C8L8J1A4
A7C8H2I4
Q8F9H6D9
Q1A9C8J9

Please help me because I really need it. Thank you.