I am (still) dealing with slow running code.

The following use "for" loops to populate cells. The first example needs
add headers to thrtee sheets based on what exists on another sheet. The
second example needs to add a formula to each row in column A that contains
values in column B.

Could someone suggest a better way to get these jobs done? Arrays?

******************
1.
For index1 = 1 To num_headers 'num headers is variable
header_val = Worksheets("sheet1").Cells(1, index1).Value
Worksheets("sheet2").Cells(1, index1).Value = header_val
Worksheets("sheet3").Cells(1, index1 + 1).Value = header_val
Worksheets("sheet4").Cells(1, index1 + 1).Value = header_val
Next

2.
For index1 = 1 To num_month_records 'variable
Worksheets("sheet1").Cells(index1 + 1, 1).FormulaR1C1 =
"=CONCATENATE(RC3,""_"",RC4)"
Next