IF statement including VLOOKUP - excel

Question

Looking for a way to do an IF cell says (this) then VLOOKUP here, IF cell says (thiselse) then VLOOKUP different area.
Might be a super obvious way to do this, so far have this:
Pretty simple but not working
Sub categoryVLOOKUP()
'IF col D says STAR then enter VLOOKUP formula into column K
'IF col D says SUN then enter other VLOOKUP formula into column K
Dim lRow As Long, lCol As Long
Dim lRow2 As Long
Dim sht As Worksheet
Set sht = ThisWorkbook.Worksheets("STARSUN")
For lRow = 2 To LastRow
If sht.Cells(lRow, 4) = "SUN" Then
sht.Cells(lRow, 10).Formula = _
"=VLOOKUP(A3&G3,OF_MOON!A:D, 4,0)"
Else
End If
If sht.Cells(lRow, 4) = "STAR" Then
sht.Cells(lRow, 10).Formula = _
"=VLOOKUP(A3&G3,OFWORLD!A:D, 4,0)"
Else
End If
Next lRow
End Sub

Answer 1

If it is getting the formula for multiple cells that is the struggle, I would recommend R1C1 formatting:
Sub categoryVLOOKUP()
'IF col D says STAR then enter VLOOKUP formula into column K
'IF col D says SUN then enter other VLOOKUP formula into column K
Dim lRow As Long, lCol As Long
Dim lRow2 As Long
Dim sht As Worksheet
Dim LastRow as long
LastRow = Cells(Rows.Count, "D").End(xlUp).Row
Set sht = ThisWorkbook.Worksheets("STARSUN")
For lRow = 2 To LastRow
If sht.Cells(lRow, 4) = "SUN" Then
sht.Cells(lRow, 10).FormulaR1C1 = _
"=VLOOKUP(R[1]C[-8]&R[1]C[-1],OF_MOON!RC:RC[3], 4,0)"
ElseIf
If sht.Cells(lRow, 4) = "STAR" Then
sht.Cells(lRow, 10).FormulaR1C1 = _
"=VLOOKUP(R[1]C[-8]&R[1]C[-1],OFWORLD!RC:RC[3], 4,0)"
End If
Next lRow
End Sub
I think this train of thought should get you started. Remember that R1C1 has to be done in reference to the active cell that the formula will go in. I may need to check the rules for referring to new sheets but again, this should get you on the right line :) hope it helps
EDIT : Also, I believe you do need to set LastRow
I have added to the code
Dim LastRow as long
and
LastRow = Cells(Rows.Count, "D").End(xlUp).Row

Answer 2

Looks like you are missing definition and value of LastRow.
Use option explicit at the beginning of your modules to enforce variable declaration. Or simply Tools -> Options -> check Require Variable Declaration. It will be done automatically.
Also I do not understand why you would even use VBA for this. Can't you just use formula
=IF(cell="SUN",1st vlookup, if(cell="STAR", 2nd vlookup,NA())
Also I suggest using INDEX + MATCH instead of VLOOKUP.
And 3rd "also": you are hardcoding the key you will be looking up for: A3&G3. Thus You will get max of 3 values from your actions: Whatever is associated with A3&G3 in OF_MOON sheet or in OFWORLD sheet or #N/A.

Answer 3

Another way to get the result as below
Sub categoryVLOOKUP()
Dim lRow As Long, lCol As Long
Dim lRow2 As Long
Dim sht As Worksheet
LastRow = Range("D" & Rows.Count).End(xlUp).Row
Set sht = ThisWorkbook.Worksheets("STARSUN")
For lRow = 2 To LastRow
If sht.Cells(lRow, 4) = "SUN" Then
Range("K" & lRow).Value = Application.WorksheetFunction.VLookup(Range("A" & lRow) & Range("G" & lRow), Worksheets("OF_MOON").Range("A:D"), 4, 0)
ElseIf sht.Cells(lRow, 4) = "STAR" Then
Range("K" & lRow).Value = Application.WorksheetFunction.VLookup(Range("A" & lRow) & Range("G" & lRow), Worksheets("OF_MOON").Range("A:D"), 4, 0)
End If
Next lRow
End Sub