output in voice

Question

i have a textbox , when i enter a single digit in it , it should read back ( i have the wave file saved for it ) 

1.if i enter three digit number for eg: 123 ..it should read as one twentythree.
2.if i enter four digit number it should split that in two digit and read it back.
3.if i enter digit like 22 it should read it as double two.




i have wav files stored for every digit.

 tell me how to split those digit ( how to write function for 1 digit, 2 digit, 3 digit 4 digit)
so that i can call them.