[pmwiki-users] fox write ptv value when file upload

[noskule]

hi list, hans

Is there a way to write a ptv if a user uploads a file via fox upload 
field? Something like

if {$$upfile_name} != "" defaultpicture={$$upfile_name}

If no upload takes place , the ptv "defaultpicture" should ne be 
overwritten.

Thanks for any hins
nos