[NTG-context] defining a command

Hello, I have this definition: \def\oneplot#1#2#3% {\placefigure [here][#3] {\bfc #2} {\hfil \scale[width=10.5cm]{#1} \hfil} } (It is modified from an example on the wiki that takes only the first two arguments). I use it like this: \oneplot % image % caption % reference {\externalfigure[Fluorita_green]} {Fluorite cleavage} {cleavage} but the reference is ignored and I get ?? in the compiled document. Could someone point out my error please? Cheers, Roger