While making the Caption = "" removes the text, if you also need to make the dimensions small (so the label is no longer taking up space) you can change the Height and Width properties.
Code:
If lbl_Slave1.Caption = "Y/N" Then
Code:
With lbl_Slave1
.Height = 1
.Width = 1
.Caption = ""
End With
End If
It is unclear when and how you are going to fire your procedure.