"Trefor" wrote...
Is it possible to check that a cell only contains Alphanumerical
(a-Z, 0-9)?

Yes. The simplest way involves using a define name, ALPHANUM defined as

={"0";"1";"2";"3";"4";"5";"6";"7";"8";"9";"A";"B"; "C";"D";"E";"F";"G";"H";
"I";"J";"K";"L";"M";"N";"O";"P";"Q";"R";"S";"T";"U ";"V";"W";"X";"Y";"Z"}

and use formulas like

=SUMPRODUCT(LEN(x)-LEN(SUBSTITUTE(UPPER(x),ALPHANUM,"")))=LEN(x)