...and select the Extrude feature and hit OK. Now go to the Expressions dialog and you will see a new Expression which indicates that it's controlling the 'suppression' status of the extrude feature and its value should be '1'.
Now just edit that Expression using an IF statement Expression, something along the lines of...
<name of suppression expression>=IF(x=<10)(0)else(1)
Note that when the value of the 'supression expression' is equal to '1', the feature will be present (unsuppressed). If the value is equal to '0', the feature will be suppressed.
John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA