Alphabets in timestamp for a flatfile

Hi

I am into a senario where in I need to have an alphabet in the end of timestamp everytime i generate an output flatfile.

Output file format is .txt

for example run1 : Output_20121707a

   run2: Output_20121707b

   run3: Output_20121807c....

I am aware of timestamp but my concern is the alphabets. How can i do it automatically.

Anand