Using 'INPUT' to get data

I am using the following to prompt for a filename but when it runs the input line the program locks


Local filename:String
Local f:TStream
Local x:Int,y:Int


filename=Input("filename to save: ")
filename=filename+".lvl"


f=WriteFile(filename)



Any ideas why this is please? With Blitz3D it gave me a prompt at the top left of the screen with the cursor but this doesnt seem to work

Thanks
Graham