Loop through first row and if Cell Value = "Item Cost" then loop through that column and carry out subtotal in blanks - excel

Question

Very new to VBA but have managed to learn a lot in the last few weeks and stitch together some code for a project at work.
I am struggling with a loop within a loop.
Essentially I want to find every column in Row 1 that has cell value of "Item Cost" then loop down through each row in that column and place a subtotal in the blanks.
Any help with a solution would be greatly appreciated. It is part of a much larger project but I am at this sticking Point.
Code:
[VBA]
Sub InsertTotals()
Dim sh As Worksheet
Dim rw As Range
Dim RowCount As Integer
RowCount = 0
Set sh = ActiveSheet
For Each rw In sh.Rows
If sh.Cells(rw.Row, 1).Value = "Item Cost" Then
Dim ThisCell As Range
Dim MySum As Double
Set ThisCell = rw.offset(-1)
nxt:
Do While ThisCell <> ""
MySum = MySum + ThisCell
Set ThisCell = ThisCell.offset(1, 0)
Loop
ThisCell.Value = MySum
If ThisCell.offset(1, 0) <> "" Then
Set ThisCell = ThisCell.offset(1, 0)
MySum = 0
GoTo nxt
End If
End If
Next rw
End Sub
[VBA]

Answer 1

I've changed the way that the start and stop of the ranges to be subtotaled were collected. Additionally, every row has a subtotal at the bottom since there is likely an empty cell there.
Sub Insert_SubTotals()
Dim sh As Worksheet
Dim rw As Long, srw As Long, col As Long
Set sh = ActiveSheet
With sh
For col = 1 To Cells(1, Columns.Count).End(xlToLeft).Column
If .Cells(1, col) = "Item Cost" Then
srw = 2
For rw = 2 To .Cells(Rows.Count, col).End(xlUp).Row + 1
If IsEmpty(.Cells(rw, col)) And rw > srw Then
'.Cells(rw, col).Value = Application.Sum(.Range(.Cells(srw, col), .Cells(rw - 1, col)))
.Cells(rw, col).Formula = "=SUM(" & .Cells(srw, col).Address(0, 0) & _
Chr(58) & .Cells(rw - 1, col).Address(0, 0) & ")"
.Cells(rw, col).NumberFormat = _
"[color5]_($* #,##0.00_);[color9]_($* (#,##0.00);[color15]_("" - ""_);[color10]_(#_)"
srw = rw + 1
End If
Next rw
End If
Next col
End With
Set sh = Nothing
End Sub
I applied a blue Accounting style number format to distinguish the subtotals from the rest of the numbers. Modify that as you see fit. The subtotals remain as =SUM(...) formulas. I've added (and commented) a line that would simply leave the values just above the formula assignment.