Computer Programming Concepts and Visual Basic David I. Schneider

202 Computer Programming Concepts and Visual Basic
FIGURE 6-10 Template for Spreadsheet
Because processing the totals for the spreadsheet involves adding columns and rows of
cells, coding is simplified by using a control array of text boxes so that an index in a
For...Next loop can step through a set of cells. A two-dimensional array of text boxes seems
natural for the spreadsheet. Unfortunately, only a single index is available for control arrays
in Visual Basic. However, a single dimensional array of text boxes can be used without much
difficulty if we define a function Indx that connects a pair of row (1 to 16) and column (1 to
6) values to a unique index (1 to 96) value. An example of such a rule would be Indx(row,column)=(row–1)*6+column.
Successive values of this function are generated by going from
left to right across row 1, then left to right across row 2, and so on.
A solution to the spreadsheet problem that uses one control array of text boxes and two
control arrays of labels follows. The text box control array txtCell( ) provides the 96 text boxes
needed for the spreadsheet cells. Because the proposed Indx function advances by one as we
move from left to right across a row of cells, the cells must be positioned in this order as they
are loaded. The label control array lblRowLab( ) provides a label for each of the rows of cells,
while label control array lblColLab( ) provides a label for each column of cells. Figure 6-11
shows the layout of the form at design time. The properties for the controls are given in Table
6.7. The Height and Width properties given for the text box will assure enough room on the
screen for all 96 cells. These dimensions can be obtained by creating a normal size text box,
then reducing its width by one set of grid marks and its height by two sets of grid marks.
FIGURE 6-11 Controls at Design Time
TABLE 6.7
Objects and Their Properties
Object Property Setting
frmSpreadsheet Caption Spreadsheet
cmdNew Caption New
cmdQuit Caption Quit
lblRowLab() Caption 1