sequential alphanumeric formula

[Rodrigues]

Hi There
I'm sure this will be trivial, but for me is a challenge.
Could someone help me with a formula to get a sequential alphanumeric numbers in excel.
Aim: get from cell A2, displaying a sequential number such as: BXCA1 ; BXCA2 ; BXCA3 ; BXCA4 ; BXCA5, etc.
Conditional, if cell on column B is empty than blank ("")
On cell A2 I have
=IF(B2="","","BXCA1")

On the rest of the cells downwards would like to get something like:
cell A3 = if(B3="","",otherwise = BXCA2
cell A4 = if(B4="","",otherwise = BXCA3
and so on.
The formula I'm working with add an extra number1, instead of
have attached a file for better illustration.
Thanks
R

 

[bosco_yip]

In A2, copied down :

=IF(B2="","","BXCA"&COUNT(B$2:B2))

Regards
Bosco

 

[Rodrigues]

Bosco
Excellent, thank you very much.
Regards
R

 

[Syedali]

=IF(A2="","",LEFT(A2,4)&ROW()-1)