Flying Days

	A	B	C
1	Inp	Out
2	123	123----	B2: =FlyingDays(A2)
3	345	--345--
4	x7	123456-
5	x15	-234-67
6	1234567	1234567
7	x	1234567

Function FlyingDays(sInp As String) As String
    Dim i           As Long

    If sInp Like Replace(Space(Len(sInp)), " ", "[1-7]") Then
        FlyingDays = "-------"
        For i = 1 To Len(sInp)
            Mid(FlyingDays, Mid(sInp, i, 1)) = Mid(sInp, i, 1)
        Next i

    ElseIf UCase(sInp) Like "X" & Replace(Space(Len(sInp) - 1), " ", "[1-7]") Then
        FlyingDays = "1234567"
        For i = 2 To Len(sInp)
            Mid(FlyingDays, Mid(sInp, i, 1)) = "-"
        Next i

    Else
        FlyingDays = "Invalid input!"
    End If
End Function

Yup -- open the VBE, Insert > Module, paste the code there.

You're welcome.

formula option unfortunately it gives missing in reverse order!
=IF(A1="",1234567,IF(LEFT(A1)="x",SUBSTITUTE(7654321-SUMPRODUCT(MID(A1,COLUMN(INDIRECT("b"&":"&CHAR(64+LEN(A1)))),1)*10^(MID(A1,COLUMN(INDIRECT("b"&":"&CHAR(64+LEN(A1)))),1)-1)),0,"")+0,A1))

	A	B
1	123	123
2	345	345
3	x1257	643
4	13456	13456
5	x234	7651
6		1234567

revised formula
=IF(A1="","1234567",IF(LEFT(A1)="x",SUBSTITUTE(1234567-SUMPRODUCT(MID(A1,COLUMN(INDIRECT("b"&":"&CHAR(64+LEN(A1)))),1)*10^(8-MID(A1,COLUMN(INDIRECT("b"&":"&CHAR(64+LEN(A1)))),1)-1)),0,""),A1&""))

	A	B
1	x123	4567
2	x345	1267
3	x1257	346
4	x13456	27
5	x234	1567
6	1234567	1234567
7	x1234567
8	367	367
9	156	156
10	x156	2347