The Tabindex number of a control determines the order in which controls are selected on a form when the user presses the tab control.

Most newbies start out by numbering the first control Tabindex 1, and then progressing through the form.

An easier way is this:

Go through the controls in REVERSE order, setting the Tabindex of each to 0 (zero). VB helpfully numbers them for you. Can be done very quickly with the mouse and one finger on the '0' key.