Hi Vishal,
Why don't you try out ABAP regular expression to validate a string conforming to a particular code mask?
Syntax for creating the regular expressions can be found in the following link:
http://help.sap.com/abapdocu_70/en/ABENREGEX_SYNTAX.htm
Once you create the regular expression for your WBS element, you can make use of the methods in the ABAP class cl_abap_matcher to verify the entered string against your regular expression.
Sample code is as given below:
DATA: matcher TYPE REF TO cl_abap_matcher,
lv_match TYPE c,
lv_regex TYPE text255, "regular expression
lv_str TYPE text255. "string to be validated
* Verify match for the string
matcher = cl_abap_matcher=>create( pattern = lv_regex
ignore_case = abap_true
text = lv_str ).
lv_match = matcher->match( ).
IF lv_match EQ 'X'.
Message 'Success'.
Else.
Message 'Fail'.
Endif.
Hope this is helpful for you in resolving your issue.
Thanks & Regards,
Sarath.