VBA to decode digits into letters

Given that A = 1, B = 2, … , Z = 26 how would you write a VBA function that decodes a string of digits into all the possible letter strings it could represent?

Thus
f(182491) = AHBDIA, AHXIA, RBDIA, RXIA

The above example gives the letter strings corresponding to (1 8 2 4 9 1), (1 8 24 9 1), (18 2 4 9 1), (18 24 9 1) respectively.