in that case your approach needs to be completely different. The actions required are:
1. search tblAssetName for a list of partial matches on name
2. note all the different related PK values
3. apply these values as a filter against the FK in your form
Code:
Private Sub btnSearch_Click()
dim rst as dao.recordset
dim db as dao.database
dim fltrStr as string
'1. search tblAssetName for a list of partial matches on name
set db=currentdb
set rst=db.openrecordset("SELECT AssetNamePK FROM tblAssetName WHERE AssetName LIKE '*" & txtSearch & "*'")
'2. note all the different related PK values
fltrstr=""
while not rst.eof
fltrStr=fltrStr & "," & rst!AssetNamePK
rst.movenext
wend
rst.close
set rst=nothing
'3. apply these values as a filter against the FK in your form
if fltrStr<>"" then
me.filter="AssetNameFK IN (" & mid(fltrStr,2) & ")"
me.filteron=true
end if
set db=nothing
End Sub