Subroutine

Hi,

How to create a subroutine in the program. I had written the program and i had written perform statement. Now i want to create subroutine in the program. what is the command we use for that.

This is my program.

REPORT ZAC_TAB23.

TYPES:

BEGIN OF TY_KNA1,

KUNNR TYPE KNA1-KUNNR,

LAND1 TYPE KNA1-LAND1,

NAME1 TYPE KNA1-NAME1,

ORT01 TYPE KNA1-ORT01,

END OF TY_KNA1,

BEGIN OF TY_VBAK,

VBELN TYPE VBAK-VBELN,

AUDAT TYPE VBAK-AUDAT,

AUART TYPE VBAK-AUART,

NETWR TYPE VBAK-NETWR,

END OF TY_VBAK,

BEGIN OF TY_VBAP,

POSNR TYPE VBAP-POSNR,

MATNR TYPE VBAP-MATNR,

ARKTX TYPE VBAP-ARKTX,

NETPR TYPE VBAP-NETPR,

NETWR TYPE VBAP-NETWR,

END OF TY_VBAP.

DATA:

ST_KNA1 TYPE TY_KNA1,

IT_KNA1 TYPE TABLE OF TY_KNA1,

ST_VBAK TYPE TY_VBAK,

IT_VBAK TYPE TABLE OF TY_VBAK,

ST_VBAP TYPE TY_VBAP,

IT_VBAP TYPE TABLE OF TY_VBAP.

• S E L E C T O P T I O N S

SELECT-OPTIONS:

SKUNNR FOR ST_KNA1-KUNNR.

• S T A R T O F S E L E C T I O N.

START-OF-SELECTION.

PERFORM GET CUSTDATA.

ENDFORM. "

Now iam getting the error that custdat is not able to interpret.

what is the command we use to create a

FORM CUSTDATA (Subroutine) in the end.