Do more than on action if and IF statement is true

Hi,
I have a macro and in it I have an if statement:
If MsgBox("Is the correct Part Number (" & aa & ") entered?", vbYesNo) = vbYes _
Then ee = Application.InputBox("Please enter Vendor Code") _
Else: Range("C1:D1").ClearContents
End If

What I want to add is that when the statement is true, after the message box appears and the Vendor code is entered, I want the macro to put this formula into Cell C6:
=IF(C4="","",(VLOOKUP(C4,STS!A6:C20000,1,TRUE)))