You can disable or grey out standard field in ME51N on certain condition. the solution you need to create Enhancement Implementation in function module MEREQBADI_FS_ITEM and create enhancement on last line and put this ABAP Code into this enhancement.

Note : That’s code will grey out automatically after user input data into field AFNAM ( Requisitioner ) and IDNLF ( Supplier Material ) .

You can change according your needed.

How to find METAFIELD

You need to know Metafield Number of standard field in ME51N. the simple method you can run function module MEMFS_BUILD_MAPPING_PO_DOC and you need to enter MMPUR_PO_DOC or MMPUR_PR_DOC into parameter IM_APPLICATION.

how to grey out standard field me51n

You can get Metafield Number from METAFIELD Column , and TABNAME MEREQ_ITEM for Standard PR field.

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