I just used
var2(0) = Trim(var2(0))
and it worked.
Is that really bad programming??
Edit:
I added it directly to the DLookup instead:
lngSiteID = Nz(DLookup("SiteID", "Table", "Field1=" & Chr(34) & Trim(var2(0)) & Chr(34)), 0)
Everything seems to be working as expected now - thank you!