regex - Access 2000 regular express #Error -

i getting error in access 2000 when using custom functions in vba , regular expressions ?

the function works 99% of time, when field null("") word #error in field ?

here expression:

(machineo?n?:?\s?\s?""?""?[0-9a-z_\.-]+)") 

the function:

public function parse(record string, pattern string) string     set parseregexp = new regexp         parseregexp.pattern = pattern         parseregexp.global = true          dim parseit matchcollection         set parseit = parseregexp.execute(record)          each parsereturn in parseit             parse = parsereturn         next parsereturn end function 

use function this:

parse(nz(record," "), pattern)