An apparatus and a method for calculating in-place pat metric addressing far a trellis processing arrangement are provided. An arrangement of cascaded multiplexers and stores receives a known input sequence of path metrics. The input sequence of path metrics is manipulated such that certain of the path metrics are delayed in the stores by a clock cycle, whilst the remaining path metrics are presented to the cascaded banks of multiplexers. In this manner, the input sequence of path metrics is continuously processed to produce a desired output sequence of path metrics. Advantageously, embodiments of the apparatus and method may be practiced on either a forward trellis or a reverse trellis.