From Xojo Documentation

Property (As String )
aClipboard.Text = newStringValue
StringValue = aClipboard.Text

Supported for all project types and targets.

The text on the Clipboard.

Sample Code

This code is in the Action event of a button. It checks the Clipboard for text. If it finds text, it assigns it to the Text property of the TextField.

Var c As Clipboard

// create an instance of the clipboard
c = New Clipboard

// check for textAvailable
If c.TextAvailable Then
// text is available, set the TextField to it
TextField1.Value = c.Text
End If

// close it