Adjust the length of the Detail section if necessary so that there is approximately $0\mathrm{.}5$ inch below the frmBillingSubform control. The Detail section should be approximately $5\mathrm{.}5$ inches.

$2.$

On the Form Design Tools Design tab, in the Controls group, click the Text Box tool $.$

$3.$

Position the pointer$$s plus symbol below the frmBillingSubform at the $5-$inch mark on the vertical ruler and aligned with the $1-$inch mark on the horizontal ruler, and then click to insert the text box control and label in the form. Don$$t be concerned about positioning the control precisely because you$$ll resize and move the label and text box later.

$4.$

Open the Property Sheet, click the label control for the text box, set its Caption property to Number of Invoices, right$-$click the border of the label control, point to Size on the shortcut menu, and then click To Fit. Don$$t worry if the label control now overlaps the text box control.

You$$ll use Expression Builder to set a Control Source property for the text box control.

$5.$

Click the unbound text box control to select it$,$ click the Control Source box in the Property Sheet, and then click the property$$s Build button to open Expression Builder.

$6.$

In the Expression Elements box, click the expand indicator next to frmVisitsAndInvoices, and then click frmBillingSubform in the Expression Elements box.

$7.$

Scroll down the Expression Categories box, and then double$-$click txtInvoiceNumCount in the Expression Categories box. See Figure $6-41.$

Figure $6-41$

Text box control$$s expression in the Expression Builder dialog box

The Expression Builder dialog box is open. The Control Source property setting is in a text box at the top of the dialog box. In the Expression Elements list, f r m Billing Subform is selected. In the Expression Categories, the calculated control is selected from the list.Enlarge Image

Instead of adding txtInvoiceNumCount to the expression box at the top, the Expression Builder changed it to $[$frmBillingSubform$].$ Form!$[$txtInvoiceNumCount$].$ This expression displays the value of the txtInvoiceNumCount control that is located in the frmBillingSubform form, which is a form object.

You need to add an equal sign to the beginning of the expression.

$8.$

Press HOME, type $=($an equal sign$),$ and then click the OK button. The Expression Builder dialog box closes, and the Control Source property is set.

Next, you$$ll add a second text box control to the main form, set the Caption property for the label control, and use Expression Builder to set the text box$$s Control Source property.

$9.$

Sidenote

Repeat Steps $2,3,$ and $4$ to add a text box to the main form, positioning the text box at the $3\mathrm{.}5-$inch mark on the horizontal ruler and approximately the $5-$inch mark on the vertical ruler, and setting the label$$s Caption property to Invoice Amount Total.

$10.$

Click the unbound text box control to select it$,$ click the Control Source box in the Property Sheet, and then click the property$$s Build button to open Expression Builder.

$11.$

In the Expression Builder dialog box, type $=($an equal sign$),$ in the Expression Elements box, click the expand indicator next to frmVisitsAndInvoices, click frmBillingSubform in the Expression Elements box, scroll down the Expression Categories box, and then double$-$click txtInvoiceAmtSum in the Expression Categories box.

$12.$

Click the OK button to accept the expression and close the Expression Builder dialog box, close the Property Sheet, and save the form.

$13.$

Click the Collapse the Ribbon button $,$ switch to Form view, and then display the record for VisitID $1453.$ See Figure $6-42.$

Figure $6-42$

Form with calculated controls

The Access form f r m Visits And Invoices with a subform is open in Layout view. Directly below the subform, there are calculated controls labeled Number of Invoices, which shows the number of invoices in the subform, and Invoice Amount Total, which shows the total of the invoice amounts in the subform.