This paper provides a framework for evaluating how market participants beliefs about foreign exchange target zones change as they learn about central bank intervention policy. We generalize the standard target-zone model to allow for intra-marginal intervention. Intra-marginal intervention implies that market participants' beliefs about the target zone can be determined from their beliefs about the likelihood of intervention. We then estimate a daily probability of intervention model for the period following the Louvre Accord. We find that the market's views of intervention target zones would have varied quite a bit over time even over this relatively stable period.