Sure. If the existing value in the column is 20 then this should be added with the value from the form field. For example, 4 + 20 = 24.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.