Function->Type..?

Not really sure what you're trying to do, and your code has a few problems. This should help:

Function cTextfield:tTxtBox( x%, y%, width%, height%, name$)
  Local name:tTxtbox=New tTxtBox
  name.x#=x%
  name.y#=y%
  Return name
End Function

Type tTxtBox
  Field x:float
  Field y:float
End Type