error setting pivot field value

I have a workbook in which users make a selection from a dropdown. This selection activates an event procedure which makes changes to several pivot tables based on the user selection. However, for some reason, when I try to establish which pivotfields to be changed my procedure fails.

Private Sub Group_Find_Top10()

Dim pt20, pt22, pt24, pt25, pt26, pt27 As PivotTable
Dim Fld1, Fld2, Fld3 As PivotField
Dim shtChrt, shtTbls As Worksheet

Set pt20 = Worksheets("Tables").PivotTables("PivotTable20")
Set pt22 = Worksheets("Tables").PivotTables("PivotTable22")
Set pt24 = Worksheets("Tables").PivotTables("PivotTable24")
Set pt25 = Worksheets("Tables").PivotTables("PivotTable25")
Set pt26 = Worksheets("Tables").PivotTables("PivotTable26")
Set pt27 = Worksheets("Tables").PivotTables("PivotTable27")
Set Fld1 = pt.PivotFields("FnctnLvl1")
Set Fld2 = pt.PivotFields("Lvl678")
Set Fld3 = pt.PivotFields("CaseTypeRU")
Set shtChrt = ThisWorkbook.Worksheets("Charts")
Set shtTbls = ThisWorkbook.Worksheets("Tables")

If shtChrt.Range("D3") = "Function" Then
With pt25
Fld3.ClearAllFilters
Fld3.CurrentPage = "(All)"
End With

and so on...

all of the pivot tables use the same data and all have at least some of the fields listed.
This process fails at the Set Fld1 = pt.PivotFields("FnctnLvl1")

I suspect that I need to be more specific with the "pt." but since those fields appear in several of the tables I would have many Set lines for the fields which I would like to avoid.

Any help would be greatly appreciated.
Thanks

romperstomper, Thanks very much for your reply. It makes perfect sense based on the information I originally provided, but, I am going to have to think about how to make it work. As you say, I will have errors when the fields don't exist but also I dont necessarily want to change all the fields even if they do exist. I guess what I am looking for is a way to change only speciic fields in specific tables. I have all the logic mapped out but I cant get the syntax correct.
for example, All of the tables have Fld1 but only pt22, pt25 and pt27 have Fld3.
When the user selects "Function" I only want to change Fld3 in pt25, Fld1 in pt26, and Fld1 and Fld3 in pt27.
and so on... the logic is complicated but what it boils down to is I only want to change some of the pivotfields in some of the pivottables based on the combination of selections made.
Thanks Again

thanks again. Thats what I did until I find a cleaner method. I just named Fld1 for pt20, Fld120 etc. So, there are 18 Set Fld stmts per Sub. Kinda Brute force and not very pretty but it does work.