增加文件上传字段的高度和宽度

i have a file upload field for upload which is inside a div which 150px x 150px and transparent(opacity:0;). i want a click on any part inside the div to pup up the file dialog box so the user can select his file to upload so i want to increase its height and width. no method of mine works. how do i solve this?i have a file upload field for upload which is