Filter table based on other table with if condition

hello,

the case is as follows:

i need to apply a filter on the table items; where it will filter based on a dimension in another table; meaning

if customer.market = "x" then item.buid = "y" else item.buid="z"

am trying to apply this on the advanced editor and since am new to DAX am its taking me forever to write the syntax correctly;

this is what i came up so far but its not working, cz its not recognizing market dim from the other table

#"Filtered Rows" = Table.SelectRows(BIDW_ITEM, each [ITEM_KEY] <> 123 and (each if BIDW_Customer[Market]="xx" then [BU_ID]="yy" else [BU_ID] = "zz")),

now i understand that the table.selectrows is being bound to scope of table item; but i tried filter and related functions and i cant seem to come up with the correct structure for the filter

am already goingin through tutorials on learning DAX from scratch, but it will need time

any help is much appreciated

regards,