Mass update through LSMW

hi friends,

I want to do mass update in material master -units of measure in additional data of material.

It is not only to change ,

it should possible to update (create, change or delete) additional data corresponding to the values in the excel file

client is preferring LSMW with Batch input method.

I think these fields are not in Tables,it's available in SMEINH structure...

how to acheive this?? how much time it will take???

thanks

raj