XML Schema regex to allow for a character to appear consecutively but reject if appears only once

The below simpleType has a pattern value = "[^*]*" , which rejects any occurrence of an asterisk in the string, which is the character we designated to blank out the corresponding database column:

<xsd:simpleType name="StringMin1Max80TypeBase">
    <xsd:restriction base="xsd:string">
        <xsd:minLength value="1"/>
        <xsd:maxLength value="80"/>
        <xsd:pattern value="[^\*]*"/>
    </xsd:restriction>
</xsd:simpleType>

Some of our simpleTypes don't have this pattern value in order to allow people to enter the * . Someone recently submitted an element with the above type that has this string: **WARNING** , so this element was rejected unintentionally. Is there a way to allow for consecutive characters like ** or ***, etc., but reject the appearance of exactly one character? I know XML Schema regular expressions do not use negative lookbehind and negative lookahead and the characters < and ? are not allowed in the pattern value.

If this is possible, how about also allowing *string* , i.e., multiple characters but not one?

Thanks a lot.