Make the upload starts with a buttom

hi I wanna know if there is a way to make the upload in flash (filereference) starts when I hit a buttom , for example the user select the file then fill the form when press the buttom ok the file that the user selected starts to upload , please somebody can tell me if there is a way to do this beacuse I am searching ,and searching … and Idon´t findo anything about it.

Thanks in advance