Code to Insert Column causes Macro to not function correctly...

Trying to create a macro to delete rows based on contents of a column, complete a few sorts, add a column and then combine contents of 3 columns into 1 for each row respectively and then subtotal based on the new combined column.

Here is what I have that works but once I try to add column, macro does not complete the sorts at all or incorrectly depending on where the code for the insertion is placed and the code is edited based on placement of the code to insert the column.

Sub Delete()
    Range("A4:J992").Select
    Range("F4:F996").Replace 0, "", xlWhole
    Range("F4:F996").SpecialCells(xlCellTypeBlanks).EntireRow.Delete
End Sub
Sub Sort2()
    Range("A4:J996").Select
    ActiveWorkbook.Worksheets(ActiveSheet.Name).Sort.SortFields.Clear
    ActiveWorkbook.Worksheets(ActiveSheet.Name).Sort.SortFields.Add Key:=Range("C4:C996"), SortOn:=xlSortOnValues, Order:=xlAscending, DataOption:=xlSortNormal
    ActiveWorkbook.Worksheets(ActiveSheet.Name).Sort.SortFields.Add Key:=Range("D4:D996"), SortOn:=xlSortOnValues, Order:=xlAscending, DataOption:=xlSortNormal
    ActiveWorkbook.Worksheets(ActiveSheet.Name).Sort.SortFields.Add Key:=Range("E4:E996"), SortOn:=xlSortOnValues, Order:=xlAscending, DataOption:=xlSortNormal
    With ActiveWorkbook.Worksheets(ActiveSheet.Name).Sort
    .SetRange Range("A4:K996")
    .Header = xlGuess
    .MatchCase = False
    .Orientation = xlTopToBottom
    .SortMethod = xlPinYin
    .Apply
    End With
End Sub

Insertion Code...

Sub InsertColumn()
    Columns("C:C").Select
    Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
End Sub

Also can not get the concatenate or =D1&" "&E1&" "&F1 to fill the new C column...the formula works for the first cell and looks correct, meaning row number within formula changes, for the next cells but the outcome is the value of the first cell C1...

Help???