Quick comment, it looks like you are comparing two strings
VBA provides a function for this, strcomp. Also string compares fail because of the prsence of non printable characters, so it is always worth doing a trim thus

strcomp(trim(range("A1").text),trim(range("A2").text)) = 0

is preferred syntax

Hi,

Here's some solution.

Firstly, declare the following variables:

' ************************* ' ************************* '
    Dim strSoughtValue As String
    Dim oTempRng As Range
    Dim strFirstCell As String
' ************************* ' ************************* '

Now, replace the following part of your code:

' ************************* ' ************************* '
    For m = 20 To .Range("F" & Rows.Count).End(xlUp).Row
       
        If Trim(Imp_Rawdata.Range("F" & c.Row)) = Trim(.Range("F" & m)) Then
            Debug.Print Imp_Rawdata.Range("F" & c.Row) & "\" & .Range("F" & m)
            .Range("F" & m & ":Z" & m).Interior.Color = 5296274
            Ref_exists = True
            Exit For
        End If
       
    Next
' ************************* ' ************************* '

with this one:

' ************************* ' ************************* '
    strSoughtValue = Trim(Imp_Rawdata.Range("F" & c.Row).Value)
   
    With .Range("F20", .Range("F" & Rows.Count).End(xlUp))
        Set oTempRng = .Find(What:=strSoughtValue, LookIn:=xlValues)
       
        If Not oTempRng Is Nothing Then
            Ref_exists = True
           
            strFirstCell = oTempRng.Address
           
            Do
                oTempRng.Resize(ColumnSize:=21).Interior.Color = 5296274
               
                Set oTempRng = .FindNext(oTempRng)
               
                If oTempRng Is Nothing Then Exit Do
            Loop While oTempRng.Address <> strFirstCell
        End If
    End With
' ************************* ' ************************* '

Best regards.

initial thought.. why are you using VBA to colour cells, and not Conditional formatting ?

25. Excel Tips - Conditional formatting