Error 'Enter a valid date (for example, 28.12.2007)' convert from excel

hi all,

error date:

when i upload excel file to SAP convert date 'Enter a valid date (for example, 28.12.2007)'

Types: begin of t_upload ,

material like BAPISITEMR-MATERIAL,

plant like BAPISITEMR-PLANT,

col1(10),

end of t_upload.

data: i_upload TYPE STANDARD TABLE OF t_upload WITH HEADER LINE,

w_upload TYPE t_upload.

data: SCHEDULE_IN like BAPISSHDIN occurs 0 WITH HEADER LINE,

FORM Get_date.

READ TABLE i_upload INDEX 1.

SCHEDULE_IN-DATE_TYPE = '1'.

CALL FUNCTION 'CONVERT_DATE_TO_INTERNAL'

EXPORTING

DATE_EXTERNAL = i_upload-col1

IMPORTING

DATE_INTERNAL = SCHEDULE_IN-REQ_DATE.

APPEND SCHEDULE_IN.

endform.

in excel formort date 12122007 (example)

pls, help me.

thanks so much/Tham.