VBA Index/match Error 1004

I'm trying to do a 2 way match using VBA, the lookup range is dynamic.

Both lastRow and lookUpvalue are set as double

lastRow = Worksheets("TPHPivot").UsedRange.Rows.Count

For i = 2 To Worksheets("RoutingSpeed_MP").Range("G" & Rows.Count).End(xlUp).Row
   
lookUpvalue = Application.WorksheetFunction.Index(Worksheets("TPHPivot").Range("E1001:P" & lastRow), Application.WorksheetFunction.Match(Worksheets("TPHEdit").Range("B" & i), Worksheets("TPHPivot").Range("D1001:D"), 0), Application.WorksheetFunction.Match(Worksheets("TPHEdit").Range("F" & i), Worksheets("TPHPivot").Range("E1000:P1000"), 0))

...

Next i

Not sure if the ranges are not written correctly. any help is appreciated. Thanks

Thanks so much!

I have made the lookUpvalue into a variant, here's the entire code:

Public Sub TPHupdate()

Dim i As Long
Dim lookUpvalue As Variant
Dim lastRow As Long
Dim endRow As Long

lastRow = Worksheets("TPHPivot").UsedRange.Rows.Count
endRow = Worksheets("RoutingSpeed_MP").Range("G" & Rows.Count).End(xlUp).Row

For i = 2 To endRow
   
    lookUpvalue = Application.Index(Worksheets("TPHPivot").Range("E1001:U" & lastRow), Application.Match(Worksheets("TPHEdit").Range("B" & i), Worksheets("TPHPivot").Range("D1001:D" & lastRow), 0), Application.Match(Worksheets("TPHEdit").Range("F" & i), Worksheets("TPHPivot").Range("E1000:U1000"), 0))

    If Worksheets("RoutingSpeed_MP").Range("G" & i).Value <> lookUpvalue Then
        Worksheets("RoutingSpeed_MP").Range("G" & i).Value = lookUpvalue
    Else
        Worksheets("RoutingSpeed_MP").Range("G" & i).Value = Worksheets("RoutingSpeed_MP").Range("G" & i).Value
        
    End If
    
Next i

Now im getting a type mismatch error on the first IF statement, comparing a value to the variant. But when I add a msgbox for the lookupvalue, it seems to be returning the correct values going through the loop. Do I have to add something to it to reformat the variant?