An apparatus for assisting a user in selecting a plurality of compatible data items comprising: a display arranged to display a plurality of dynamic display regions (302a-f) each dynamic display region being associated with a respective set of data items for display, the data items being associated with compatibility information, wherein the data items in each data set can only be selected in allowed combinations and the compatibility information indicates which items in each data set are compatible with which items in the other data sets; and an input unit arranged to receive a user selection of a data item for display in a dynamic display region, wherein the dynamic display regions (302a-f) are independently selectable using the input unit; wherein, when a data item is selected for display in a given dynamic display region, the display is updated to display a respective data item which is compatible with the selected data item in each of the other dynamic display regions (302b-f); and wherein, following selection of the data item in the given dynamic display region, and subsequent selection of an incompatible data item in a further dynamic display region, the display is updated to display a compatible data item in the given dynamic display region, wherein the incompatible data item is not compatible with the data item and the compatible data item is compatible with the incompatible data item, wherein the display is further arranged to display a plurality of locking regions (308a-f), each locking region (308a-f) being associated with a respective one of the plurality of dynamic display regions (302a-f), and wherein the input unit is further arranged to detect a selection by the user of a locking region associated with the given dynamic display region to lock the given dynamic display region; and wherein, once the data item is selected for display in the given dynamic display region and once the selection by the user of the locking region associated with the given dynamic display region is received, only those data items in other sets that are compatible with said data item are available for selection in the other dynamic display regions (302b-f). a display arranged to display a plurality of dynamic display regions (302a-f) each dynamic display region being associated with a respective set of data items for display, the data items being associated with compatibility information, wherein the data items in each data set can only be selected in allowed combinations and the compatibility information indicates which items in each data set are compatible with which items in the other data sets; and an input unit arranged to receive a user selection of a data item for display in a dynamic display region, wherein the dynamic display regions (302a-f) are independently selectable using the input unit; wherein, when a data item is selected for display in a given dynamic display region, the display is updated to display a respective data item which is compatible with the selected data item in each of the other dynamic display regions (302b-f); and wherein, following selection of the data item in the given dynamic display region, and subsequent selection of an incompatible data item in a further dynamic display region, the display is updated to display a compatible data item in the given dynamic display region, wherein the incompatible data item is not compatible with the data item and the compatible data item is compatible with the incompatible data item, wherein the display is further arranged to display a plurality of locking regions (308a-f), each locking region (308a-f) being associated with a respective one of the plurality of dynamic display regions (302a-f), and wherein the input unit is further arranged to detect a selection by the user of a locking region associated with the given dynamic display region to lock the given dynamic display region; and wherein, once the data item is selected for display in the given dynamic display region and once the selection by the user of the locking region associated with the given dynamic display region is received, only those data items in other sets that are compatible with said data item are available for selection in the other dynamic display regions (302b-f).