In the cell $B$2:
=EPMSelectMember(;"R_R205_01_05";;"WBS")
If you double click this cell you will be able to select another WBS member.
The formula: =EPMDimensionOverride("000";"ASSET_ITEM";"WBS_AST_ITEM="&$B$2)
Will be:
=EPMDimensionOverride("000";"ASSET_ITEM";"WBS_AST_ITEM=R_R205_01_05")