You don't say where you getting these symbols from, so I'll just show you the
code you need using an ampersand. You can use Windows Character Map to find
them or insert them from another source.

Private Sub InsertAmpersand_Click()
 Screen.PreviousControl = Screen.PreviousControl & "@"
 Screen.PreviousControl.SetFocus
End Sub

You can return focus to the textbox involved with

Screen.PreviousControl

but you can use it with SelStart to send the cursor to the end of the data
after the insertion, so you need to do this for each possible textbox that
you'll be using this with:

Private Sub TextBox1_Enter()
 TextBox1.SelStart = Nz(Len(Me.TextBox1), 0)
End Sub

Private Sub TextBox2_Enter()
 TextBox2.SelStart = Nz(Len(Me.TextBox2), 0)
End Sub

and so forth. Enter data in whatever field you need to, then when necessary,
click on the insert button, and the special character, in this case an
ampersand,   will be inserted in that field and the cursor will return to the
end of the data in the field, ready for the next character.