VBA type Mismatch error,how can I be sure I'm defining the right value type to variables?

Question

I'm trying to compare an String value and add a String result from that String Value, it throws an error type 13, I believe the error relies in the "Range" property,it works If I don't define an range and leave a single Cell value, but I need to check the same logic for a certain range.

Sub Vars()

'myVar = 20'
'MsgBox myVar'

Dim currencyVar As Double

Dim locationRange As String
Dim RangeResult As String

locationRange = Application.Sheets("Sheet4").Range("F3:F19")
RangeResult = Sheets("Sheet4").Range("G3:G19")

Debug.Print (locationRange)

mainXlookup = WorksheetFunction.XLookup(Sheets("Sheet4").Range("b3:b19"), Sheets("Sheet3").Range("b2:b18"), Sheets("Sheet3").Range("c2:c18"), "Not in project")

Sheets("Sheet4").Range("f3:f19") = mainXlookup


If locationRange = "Bethesda" Then
    
    RangeResult = "In-Range"
    
End If

End Sub