Function fSetFontBold(stControlName As String)
Const cBold =  700 
Const cNormal =  400 
    On Error Resume Next
    With Me(mstPrevControl)
        .FontWeight = cNormal
        .ForeColor =  1279872587 
    End With
    mstPrevControl = stControlName
    With Me(stControlName)
        .FontWeight = cBold
        .ForeColor =  0 
    End With
End Function

Function fRemoveFontBold()
Const cNormal =  400 
    On Error Resume Next
    With Me(mstPrevControl)
        .FontWeight = cNormal
        .ForeColor =  1279872587 
    End With
End Function

Private Sub Поле3_MouseMove(...)
    Me.Поле3.OnMouseMove = fSetFontBold("Поле3")
End Sub