I keep trying different scenarios and came up with this. Seems to work so far.
Hope I didn't waste your time.
Thank you for listening. Hope this helps someone else too.
Sub pd_BiMonth() ' bi monthly'makes the nD1 and nD2 text input entries day captions Bold when the check box is active
Dim D, x As Integer
Dim nD1 As Variant
Dim nD2 As Variant
Dim myDate As Date


    With ufCal
        nD1 = InputBox("Please enter the day of the month your first payday lands on", "First PayDay of Month")
            If nD1 = "" Then Exit Sub
        nD2 = InputBox("Please enter the day of the month your second payday lands on", "Second PayDay of Month")
            If nD2 = "" Then Exit Sub
            
         myDate = .uMonth.Caption & "-1-" & .uYear.Caption
   
         D = FirstWeekDayOfMonth(myDate) - 1
         
         D1 = D + nD1
         D2 = D + nD2
         
        For x = 1 To 42
            If x = D1 Or x = D2 Then
            .Controls("dnum" & x).Font.Bold = True
            .Controls("dnum" & x).Font.Size = 11
            Else
            .Controls("dnum" & x).Font.Bold = False
            .Controls("dnum" & x).Font.Size = 9
            End If
        Next x
            
    End With
End Sub