How to set .Count function to exclude headers? - vba

Question

I am trying to make a sub where the macro counts all the rows containing data (it isn't a set amount, it varies) and then picks a random number between 6 (to exclude headers) and the number of counted rows and highlights the corresponding row. Unfortunately the code I've been working on doesn't do what I need it to do. It does select and highlight a random row, but it selects empty rows too, not only the ones with data. Any ideas where I went wrong?
Sub RandomRow()
Dim mrg As Worksheet
Dim Count As Integer, myRange As Range
Set mrg = ActiveWorkbook.Sheets("Merged")
mrg.Range("A6:K200000").Interior.Color = RGB(255, 255, 255) 'reset cell colours
Set myRange = mrg.Columns("A:A")
Count = Application.WorksheetFunction.CountA(myRange)
myValue = Int((Count * Rnd) + 6) ' Generate random value between 6 and the number of filled rows'.
mrg.Range("A" & myValue).EntireRow.Interior.Color = RGB(255, 255, 153) 'highlight a random row
End Sub

Answer 1

The current value you have for count is misleading. Say it is 20, and the rows extend to 200; you cannot use the value 20 to identify the occupied rows amongst the 200 (unless you created a map/array to store all of the occupied row-numbers, and then choose randomly from these).
You could still determine the CountA if this information is useful to you, but not as part of the random selection process. Better to just find where the last occupied cell is, using End(xlUp).
Now you know the range containing the occupied cells and can choose randomly between these rows. Repeat the generation of a random number until you discover a cell/row that is not empty.
Sub RandomRow()
Dim wsMerged As Worksheet
Dim myRange As Range
Dim count As Long
Dim randRow As Long
Dim occupied As Boolean
Set wsMerged = Worksheets("Merged")
wsMerged.Range("A6:K200000").Interior.Color = RGB(255, 255, 255) 'reset cell colours
Set myRange = wsMerged.Columns("A:A")
'count = Application.WorksheetFunction.CountA(myRange)
count = Range("A200000").End(xlUp).Row - 6
Randomize 'necessary when using Rnd()
Do
randRow = CLng((count * Rnd()) + 6)
'if the cell isn't empty
If wsMerged.Range("A" & randRow).Value <> "" Then
'flag that we are done
occupied = True
wsMerged.Range("A" & randRow).Resize(1, 11).Interior.Color = RGB(255, 255, 153)
End If
Loop While Not occupied
End Sub
To clear cell colours I would set .Interior.ColorIndex = xlColorIndexNone.

Answer 2

At first MyValue is not declared.
Dim MyValue as Long
Now, its better. Secondly, your macro highlight all row, but clear colors only from A to K column. You would rather highlight first 11 columns, wouldn't you?
mrg.Range("A" & myValue).Resize(1, 11).Interior.Color = RGB(255, 255, 153)
And, to answer your question, set myRange like that:
Set myRange = mrg.Range("A6:A200000")
Then your Count worksheet function will not count headings actually. I hope, this helped.