[NTG-context] eating up &

I want to do something with & in tables (making it an active column separator). Now I have a macro with two arguments for parameters in Context style: \def\starttablex{\dodoubleargument\dostarttablex} \def\dostarttablex[#1][#2]{% Now for input: \starttable[][] & ... all is well, but for input: \starttable[] & ... the ampersand appears to be eaten up by the double argument expansion. How can I prevent that, letting & end the parameter scanning and using it as the first input? Hans van der Meer