If loop embedded in for loop

I'm setting up a budgeting spreadsheet using google sheets. I have written code so that when my budget is updated on the dashboard sheet, the historical budget on a separate sheet is updated.

I've got the following section of code working, which checks whether the cell that's been changed is in the correct region to be a budget figure.

The code then takes the budget value and budget category.

I then want to search column C in my 'Historical Budget' sheet for the correct category, search row 4 of this sheet for the relevant month and update the cell with the budget value.

var range=e.range
var row = e.range.getRow();
var col = e.range.getColumn();
var sheetname = e.range.getSheet().getName();
var ss = SpreadsheetApp.getActiveSpreadsheet(),
    sheet = ss.getActiveSheet()

if  (sheetname == "Dashboard"){
            if(col == 3)
            {
              if(row>=9)
              {
                if(row<=40)
                {
                 var budgetvalue = range.getValue();
                 var budgetcategory = sheet.getRange(row,col-1).getValue();

// For & If loops here

}}}

I'm new to google script coding, so I'm sure the code above isn't the most efficient. Please do let me know if anyone spots any glaring inefficiencies!

Thanks in advance!