VBA Randomize values from 1 to 30 thereby skipping manually entered values - excel

Question

For the first 15 ranks, I want to manually enter the values in B2:P11. For ranks 16 to 30, I want to randomize these values using an Excel VBA button, with the following code:
Sub rand_group()
Dim i As Long
Dim j As Long
Dim myFlag(1 To num_man)
Dim s_group As Worksheet
Set s_group = Worksheets("group")
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Randomize
s_group.Cells.Clear
s_group.Range("A1") = "group_id"
For i = 1 To num_group
s_group.Cells(i + 1, 1) = i
Next i
For i = 1 To num_man
s_group.Cells(1, i + 1) = "m_rank" & i
Next i
For i = 1 To num_group
For j = 16 To num_man
myFlag(j) = False
Next j
For j = 16 To num_man
Do
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myNum = Int((num_man - 1 + 1) * Rnd + 1)
Loop Until myFlag(myNum) = False
s_group.Cells(i + 1, j + 1).Value = myNum
myFlag(myNum) = True
Next j
Next i
End Sub
However, these random values should neglect the manually entered values in B2:P11
How can I change the code to fix this?
Screenshot of the excel file is displayed below:
I want to manually fill values from B2 to P11
Thank you in advance for your response!
Michiel

Answer 1

To fill in the random section of the grid, the myFlag array is not needed. Just use the cell coordinates to set the random values. Also remove the Clear call since that clears the entire sheet.
To prevent duplicate numbers in a row, use the excel CountIf function in a loop until a unique random number is found.
Here is the updated code. It can be run multiple times without affecting the manual data.
Sub DoRand()
Dim i As Long
Dim j As Long
Dim s_group As Worksheet
Set s_group = Worksheets("group")
num_group = 10
num_man = 30
Randomize
's_group.Cells.Clear ' clear sheet
' build table
For i = 1 To num_group ' group id
s_group.Cells(i + 1, 1) = i
Next i
For i = 1 To num_man ' column names
s_group.Cells(1, i + 1) = "m_rank" & i
Next i
' fill in random numbers
For i = 1 To num_group 'row
For j = 16 To num_man 'column
Do While True
n = Int((num_man) * Rnd + 1) ' get random number
cnt = Application.WorksheetFunction.CountIf(Range(s_group.Cells(i + 1, 2), s_group.Cells(i + 1, j)), "=" & n) ' check if number in row
s_group.Cells(i + 1, j + 1).Value = n ' set cell value
If cnt = 0 Then Exit Do ' if unique in row, go to next cell
Loop ' not unique, try new random value
Next
Next
End Sub