Excel VBA: Merge and Center Cells Based on Date Values in Row Below

Hi all,

I'm using the following code (found here: http://="http://stackoverflow.com/qu...n-user-input"]) populate dates in row 13 for a dynamic Gantt Chart...

Sub Date_Fill()
    Dim projEndDate As Date
    Dim projStartDate As Date
    Dim projDuration As Integer
    projStartDate = Range("C9").Value
    projEndDate = Range("C10").Value
    
    With Worksheets("ProjectTacticalGanttChart")
        Set SourceRange = .Range("I13")
        SourceRange.Value = projStartDate
        Set fillRange = .Range(SourceRange, Cells(SourceRange.Row, SourceRange.Column + projEndDate - projStartDate))
        SourceRange.AutoFill Destination:=fillRange, Type:=xlFillDays
    End With
End Subto

It works perfectly to display daily dates in the mm/dd format. Now I want to have an overarching month/year displayed over the entire range for any particular month by merging and centering the cells above the month's dates the above code populates, and pull in the month/year formatted as mmm-yyyy. I've attached a mock up I did manually to help convey the desired result.

Any help is appreciated as always. Please let me know if you have any questions or need clarification.

Thanks so much!
Chris