error TZReadOnlyQuery with MYsql Variables in Delphi5

[KAYAALP]

hello everybody,
i want to execute this sql (MySql 4.0x) with TZReadOnlyQuery id Delphi5

SELECT @n := @n+1 AS rownum, thing, arms, legs FROM limbs

but i get this error : "incorrect token followed by ':'"

i think that, the sql parser looks for a parameter after the ':'
how can i solve the problem?

[mdaems]

Set ParamCheck Property to 'False'. The query will not be scanned for ':'.

Mark

[KAYAALP]

thank you so much