Hello Sai,
DMEE provides many conversion functions to convert internal values of DMEE-tree component variables into their required output format. However, as far as I know, there are no standard routines that handle such specific cases. So, I suggest to create a dedicated FM that will check the bank account of your vendor for non-numeric symbols and replace them with some constant value (e.g. '1').
Please get in touch with ABAP developer to check on this issue or search SCN forum for topics like "Replace Non-Numeric Characters with a Numeric Character in a String" for relevant information if you decided to write this FM yourself.
Best regards,
The Wirtschaftsmann