Custom Table Entries will need to checked against the Standard Table Entries (SKA1)

Hello,

I want to create one Custom table which contains GL (SAKNR). While Creating new entries in this Custom table, Needs to be checked against the SKA1 Entries.

For this, i had created TMG and used Event 05, and written below code in the FORM.. End FORM.

   DATA ls_ska1 TYPE ska1.

   SELECT SINGLE ktopl saknr INTO ls_ska1 FROM ska1 WHERE saknr = zzzzgl-saknr.

   IF sy-subrc NE 0.

     MESSAGE 'Invalid Data' TYPE 'E'.

   ENDIF.

It is working fine for single Entry, but my Requirement is, need to check for Multiple Entries.