TextArea.ScrollPosition

From Xojo Documentation

This method uses a getter/setter (see Assigns) and acts like a property.

Property (As Integer )
aTextArea.ScrollPosition = newIntegerValue
or
IntegerValue = aTextArea.ScrollPosition

Supported for all project types and targets.

Use to get or set the topmost visible line (zero-based).

Notes

Read ScrollPosition to determine the first visible line; write to ScrollPosition to scroll the control. Setting ScrollPosition to the last line or beyond the last line will simply move the vertical scrollbar's thumb to the bottom, not necessarily displaying the last line at the top of the control.