Tabstrip - active tab

How am I suppose to make my tab being active if my textbox is initial?

Here is my codes and what I want to do:

MODULE USER_COMMAND_9000 INPUT.

IF SY-UCOMM = 'BACK'.
  LEAVE PROGRAM.
ELSEIF SY-UCOMM = 'EXIT'.
  LEAVE PROGRAM.
ELSEIF SY-UCOMM = 'CANCEL'.
  LEAVE PROGRAM.
ELSEIF SY-UCOMM = 'SAVE'.

  IF IO_NAME IS NOT INITIAL AND IO_AGE IS NOT INITIAL AND IO_GENDER IS NOT INITIAL.
  PERFORM INSERT_TABLE.

  ENDIF.
  IF IO_NAME IS INITIAL .
      MESSAGE E004(ZMSG02).

*Add codes to make the first tab active* 

  ELSEIF IO_AGE IS INITIAL.
    MESSAGE E005(ZMSG02).

*Add codes to make the second tab active* 

  ELSEIF IO_GENDER IS INITIAL.
    MESSAGE E006(ZMSG02).

*Add codes to make the third tab active* 

    ENDIF.
ENDIF.

ENDMODULE. "USER_COMMAND_9000 INPUT

What code am I suppose to add for my codes of my tabstrips?