User Specified Donation Amount - Google Checkout

[urgeinteracive]

Hi - I recently purchased the Pro version for a non-profit client and am attempting to setup 3 levels using Google Checkout. Level 1 has set donation amounts ($10, $25, $50) to have 30 day access to the site - this is super easy. Level 2 needs to accept any donation amount above $60 for 30 day access. (eg Enter your donation amount $___.00) and Level 3 is monthly recurring billing for $5, $10, etc options in addition to another "Enter your donation amount $___.00) option to be billed monthly. My question is how do I NOT set a specific dollar amount and let the subscriber choose their own amount for both a one-time payment and a recurring payment? I can't seem to find an exact answer in the forums nor figure it out when creating the buttons. Can someone help me!? THANK YOU!!!!