Change your UPDATE command: the syntax isn't even close!
UPDATE Clients SET MyColumn=MyValue, MyOtherColumn=MyOtherValue WHERE Club LIKE '%xxx%'
Is the general syntax you are looking for, but please, don;t do it like that! Do not concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Use Parametrized queries instead.
And then look at the rest of your code: since you almost certainly copy-n-pasted that from elsewhere, the rest of your application is wide open to anyone who "wants a laugh" to destroy your DB just by typing in your text boxes...