Dear Prabhav,
First did you try putting a breakpoint in the method - OVERRIDE_EVENT_OVP.
May be you can write below code in that.
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IO_OVP is importing parameter in the above method. So you can use the same.
/scmtms/cl_helper_ui=>generate_dialog_simple(
io_ovp = io_ovp
io_comp = me ).
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or
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lo_event->mv_event_id EQ cl_fpm_event=>gc_event_open_dialog_box.
lv_area_id = get_target_page( io_event = lo_event ).
/scmtms/cl_ui_dispsett=>attach_button_to_ovp( lv_area_id ).
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Thanks,
Bharath.K