Excel 2007 : split string

Helo
Gurus

first thanks for all the help this forum is extending and all those gurus who are helping

please advice how do i split a dynamic strng

when i say dynamic it means that i get different values in the cell

like this in the drop down
user selects only one of the list

ABCDEF,1234
ABC,2543
2543
ABCDEFGH,2437

...........

now

i want to split the string to have
BAS:THIS IS A FORMULA IN SAP

IF user selects ABCDEF,1234
BAS(ABCDEF),1234

if user selects ABC,2543
BAS(ABC),2543

IF user selects
2543
then
just 2543


thanks

Perhaps:

=IF(ISNUMBER(A1+0),A1,"BAS("&SUBSTITUTE(A1,",","),"))