How do I to insert a ‘tick box’ into a cell – a box that when selected inserts a cross, and when selected again it can be removed.

Hi Loreen, Thanks for the post, in answer to your question, inserting a tick box, follow these steps:
To create a check box follow these steps;
Open your worksheet
Go to View>Toolbars, and choose Forms.
Click the Check Box tool once, and click and drag somewhere near A1 in the worksheet to draw a check box.
When you release the mouse, click the Forms toolbar's Control Properties tool, or right-click the new check box, and choose Format Control.
(To take things a little further; Are you looking for a great way to get a 'Yes' or 'No' decision from an end user using Excel?)
Select the Text label and change it to text of your choice, let’s say for example the question is; Are you in the company pension scheme, click for Yes or leave blank for No, change the text to read; “Pension Scheme?”
So if your user selects the box, the answer is Yes. Now we can store the result of the decision as a value in a cell and use that value in our code or calculations.
Our first task is to tell Excel where to store the check box's "state." Right Click on the check box and click the Format Control option, On the Control tab, enter A1 in the Cell Link field, and click OK.
Now when you select the check box, you'll see the value in A1 change to TRUE when checked and to FALSE when unchecked. You can use that value in your formulas. For example, you can display a custom message with a formula such as the following:
=IF(A1,"Checked message","Unchecked message")
By the way, the check box Control Properties also let you set the initial value (state) for the check box. If you choose Mixed, the check box will initially appear greyed out and return a value of #N/A to the linked cell, which tells you that the item is neither checked nor unchecked.

If this has been useful to you, please click the Resolved link, best regards Pete

Sorry, somehow clicked the Submit button twice - Pete