Hi,
FIELD-SYMBOLS: <f_action> TYPE godynpro-action.
FIELD-SYMBOLS: <f_refdoc> TYPE godynpro-refdoc.
FIELD-SYMBOLS: <f_bwart> TYPE godefault_tv-bwart.
FIELD-SYMBOLS: <f_matnr> TYPE goitem-matnr.
FIELD-SYMBOLS: <f_matdoc> TYPE godynpro-mat_doc.
FIELD-SYMBOLS: <f_fyear> TYPE godynpro-doc_year.
ASSIGN ('(SAPLMIGO)GODYNPRO-ACTION') TO <f_action>.
ASSIGN ('(SAPLMIGO)GODYNPRO-REFDOC') TO <f_refdoc>.
ASSIGN ('(SAPLMIGO)GODEFAULT_TV-BWART') TO <f_bwart>.
ASSIGN ('(SAPLMIGO)GOITEM-MATNR') TO <f_matnr>.
ASSIGN ('(SAPLMIGO)GODYNPRO-MAT_DOC') TO <f_matdoc>.
ASSIGN ('(SAPLMIGO)GODYNPRO-DOC_YEAR') TO <f_fyear>.
You can do like this..in BADI or User exit to get screen values
Regards
Tejas