All right, in looking at your data and reading your post I think I understand.
Try this in your query:
AND IIF([Forms]![frmarchivesearch]![txtinvdatefrom] Is Null, nz((tblArchive.DateFrom),"0") like "*", (tblArchive.DateFrom) Like "*" & [Forms]![frmarchivesearch]![txtinvdatefrom] & "*"
What...