[galaxy-dev] Bowse button on upload data tool page...

Hi, how is the "Browse..." button implemented on the data upload tool page? When you click on it you get a new window appearing so you can select files to upload. Does anyone know where is the "Browse..." button is defined/implemented in the code? I thought it would be in "./templates/webapps/galaxy/tool_form.mako" but can't see any references to it Thanks foir any help Neil