Dim priceRange As Range
startRowNum = GetFirstRow(StartTime)     << THIS TAKE 10 SECONDS
endRowNum = GetLastRow(endTime)         << THIS TAKE 10 SECONDS
Set priceRange = Range(Cells(startRowNum, 4), Cells(endRowNum, 4))
targetRange.Offset(0, 2).Value = Application.WorksheetFunction.Max(priceRange)
targetRange.Offset(0, 3).Value = Application.WorksheetFunction.Min(priceRange)

Function GetFirstRow(T As Date) As Long

'Starts at FirstRow and returns the first row where the time is greater than T1.

Dim currentRow As Long
Dim CompareTime As Date
Dim CompareDate As Date

currentRow = 4 'Start at row4 due to headers.

Do While (IsDate(Cells(currentRow, 2)))
    CompareDate = Cells(currentRow, 2)
    CompareTime = Cells(currentRow, 3)
    marketTime = CompareDate + CompareTime
  If (marketTime >= T) Then Exit Do
  currentRow = currentRow + 1
Loop

GetFirstRow = currentRow

End Function