Some forms can only be submitted by paid-up members. Others who answer to 'no' to the question which asks whether they are current members, or whether they have paid their fees, will be redirected to the membership sign-up page. To create such a redirect, make a select list for the field asking whether the membership is current; and make sure the machine name, or key, for this field is membership_current. The field should be a select list, and one of the options in the list should have the machine name 'no' (without quotation marks). This only works on webforms, and only works where for a drop-down list where the machine name of the field 'membership_current' and the option 'no' are spelled exactly in this way. When those conditions are met, any person who selects 'no' from that drop-down list should be automatically redirected to the Individual Membership form.
In case a user is not redirected (for example where Javascript is disabled in the browser) or succeeds in attempting to submit a form without answering 'Yes' (or more precisely, giving an answer to the membership_current field whose machine name is 'yes' in lower case without the quotation marks), the form submssion will fail with the message 'The form can only be submitted if you answer yes when asked whether your membership is current.'