Assigning a named Range value to a variable

I am building a workbook that contains test results for control parts that company I work for manufactures. There are 28 parts with 6 performance criteria each.

I am trying to "grab" a value for each part and parameter to be used in conditional formatting formula: =rnSource +/- (rnSource*Tolerance).

Each part number has a SN and 6 test point results (TPs). I named the ranges (single cells) as SN_TPx (x, being 1, 2, 3,...6). These named cells are in a different worksheet than conditional formatting target worksheets (28 of these, 1/SN). Individual worksheet contain current run test results (sheets are named using a SN). Below code worked when I used SN_TPx in place of rnSource.

Reason: I can reuse the code with modification of one "Dim" rather than copy/paste code 168 times and changing cell references throughout the code (8 occurrences). I have seven other product lines to apply this to.

In my code I attempted: Dim rnSource As Range, then assign SN_TPx to rnSource using Set rnSource = SN_TPx. This results in:

Run-time error '424': Object required

I tried rnSource =:
SN_TPx.Value - '424' error

Range(SN_TPx).Value:

Run-time error '1004': Method 'Range' of object '_Global' failed

Range("SN_TPx").Value
Code runs but my Conditional Formatting formula results in:

Cell Value < rnSource-(rnSource*Tolerance)

which doesn't seem to return value of SN_TPx rather rnSource text (formatted value font is not affected)

Worksheet("Sheet3").Range(SN_TPx)

Compile error: Sub or Function not defined (Worksheet)

Worksheets("Sheet3").Range("SN_TPx")

Run-time error '9': Subscript out of range

Sub TP1_CondFormat_AV()
'***   Attempt to handle ranges (source and target) of CondFormat by setting dims and ranges upfront_
' then execute CondFormat routine for each set of dims and ranges

With ActiveSheet

'** par - define needed variables
Dim r1 As Range
Dim r2 As Range
Dim TP1_Range As Range
Dim TP2_Range As Range

'Dim rnSource As Variant ' fail
'Dim rnSource As Integer ' fail
Dim rnSource As Range
Dim rnTarget As Range
Dim wsSource As Worksheet
Dim wsTarget As Worksheet

'*** par - create a range called "rnTarget" which consists of r1 and r2 ranges
Set r1 = Range("L2:L4")
Set r2 = Range("L7:L1048576")
Set rnTarget = Union(r1, r2)
rnTarget.Name = "TP1"    'Name the rnTarget as "TP1"

Set rnSource = Range(SN_TP1).Value  '== troubleshooting, unable to point rnSource to "SN_TP1" value

End With

rnTarget.FormatConditions.Add Type:=xlCellValue, Operator:=xlLess, _
        Formula1:="=rnSource-(rnSource*Tolerance)"
rnTarget.FormatConditions(rnTarget.FormatConditions.Count).SetFirstPriority
    With rnTarget.FormatConditions(1).Font
        .Bold = True
        .Color = -4165632
        .TintAndShade = 0
    End With
    rnTarget.FormatConditions(1).StopIfTrue = False
    rnTarget.FormatConditions.Add Type:=xlCellValue, Operator:=xlGreater, _
        Formula1:="=rnSource+(rnSource*Tolerance)"
    rnTarget.FormatConditions(rnTarget.FormatConditions.Count).SetFirstPriority
    With rnTarget.FormatConditions(1).Font
        .Bold = True
        .Color = -16776961
        .TintAndShade = 0
    End With
    rnTarget.FormatConditions(1).StopIfTrue = False

End Sub