My Macro stinks

[KronkeyDong]

I really didn't want to bug anybody about help with this, but I can't figure it out and I've been working on it for a week now and I'm feeling pretty dumb. I'm using Excel 2003 SP3. I'm collecting data and only want to use the data as the values are increasing. Once the values start decreasing they are not of interest. The goal is to cut out the useful data (make them into zeros). To add difficulty though there are zeros within the data and these are to be ignored and the previous value (a column to the left) that isn't a zero is to be compared to see if the data is increasing or decreasing. The data is column Q to column AI in multiple rows (each row isn't compared though). Here is a 10 cell wide example of what the goal is

0, 100, 200, 0, 0, 0, 300, 0, 100, 50 (initial)
0, 100, 200, 0, 0, 0, 300, 0, 0, 0 (final)

I'm pretty sure my current attempt doesn't account for the zeroes that well, but I'm not sure because it keeps crashing like a son of a gun.

Sub Jc_Ic_autocutoffzz()
Dim zp As Integer
Dim z2 As Integer
Dim x As Integer
Dim jcrit1 As Integer
Dim jcrit2 As Integer
Dim jcrit3 As Integer
For zp = 3 To 200
    If Cells(zp, 17) = 0 Then
        Cells(zp, 17) = 0.000001
    Else
        Cells(zp, 17).Value = Cells(zp, 17)
    End If
    For jcrit2 = 18 To 36
        If Cells(zp, jcrit2) = 0 Then
            jcrit2 = jcrit2 - 1
        End If
        Next jcrit2
            x = 18
            Do While x < 37
            jcrit3 = x - 1
            If Cells(zp, x) < Cells(zp, jcrit3) Then
                 Cells(zp, x + 20).Value = 0
            Else
                 Cells(zp, x + 20).Value = Cells(zp, x)
            End If
            x = x + 1
            Loop
            For z2 = 17 To 36
                 If Cells(zp, z2) = 0.000001 Then
                     Cells(zp, z2 + 20).Value = 0
                 End If
            Next z2
        Next zp
End Sub

Yep, I'm going bonkers.

[mdmackillop]

Option Explicit
Sub Test()
    Dim Endd As Range, rng As Range, cel As Range, c As Range
    Dim i As Long, x As Long
    For i = 1 To 2
    x = 0
    Set Endd = Cells(i, 1).End(xlToRight)
    Set rng = Range(Cells(i, 2), Endd)
    For Each cel In rng
        x = x + 1
        If cel < Application.Max(Cells(i, 1).Resize(, x)) And cel <> 0 Then
            For Each c In Range(cel, Endd)
                c.Value = 0
            Next
        End If
    Next
    Next
End Sub

[mdmackillop]

For data starting in Column Q

Option Explicit
Sub Test()
    Dim Endd As Range, rng As Range, cel As Range, c As Range
    Dim i As Long, x As Long
    For i = 1 To 2  '<=== Set required number or rows
    x = 0
    Set Endd = Cells(i, "Q").End(xlToRight)
    Set rng = Range(Cells(i, "R"), Endd)
    For Each cel In rng
        x = x + 1
        If cel < Application.Max(Cells(i, 1).Resize(, x)) And cel <> 0 Then
            For Each c In Range(cel, Endd)
                 c.Value = 0
             Next
        End If
    Next
    Next
End Sub