When you select a block of data within a spreadsheet and select Graphs of Block Data - Histogram: Entire Columns from the Graphs menu (or right-click and select Graphs of Block Data - Histogram: Entire Columns from the resulting shortcut menu) a 2D histogram with a fitted normal curve is created for each variable (column) represented in the block (e.g., not just the values highlighted in the block but all the values in the entire column), and is then plotted in a separate graph window.
To create a histogram for each (case) row represented in the block, select Graphs of Block Data - Custom Graph for Entire Row from the Graphs menu.
If you want to create a multiple histogram to allow for comparisons between the frequency distributions of values in block columns,
select Graphs of Block Data - Custom Graph for Entire Column from the Graphs menu,
click the More button on the Select Graph dialog,
and select the Single Window (Overlaid) option button.
For more information on 2D histograms, see Graphs of Input Data - Histogram by... or 2D Histograms.