How to do Vlookup when range is dynamic

[siddo]

I have 2 tabs in an excel sheet and I have stored the last row of the column in LR1 variable I now want vlookup to perform the action everytime and take the range from "A1" TO "ALR1"

ActiveCell.FormulaR1C1 = "=VLOOKUP(RC[-1],ProblemID_afterDupl!R2C1:R46C2,2,0)"

 

[siddo]

I have 2 tabs in an excel sheet and I have stored the last row of the column in LR1 variable I now want vlookup to perform the action everytime and take the range from "A1" TO "ALR1"

ActiveCell.FormulaR1C1 = "=VLOOKUP(RC[-1],ProblemID_afterDupl!R2C1:R46C2,2,0)"

ActiveCell.FormulaR1C1 = "=VLOOKUP(A1,ProblemID_afterDupl!$A$2:$B$" & LR1 & ",2,0)"

Tried doing this however unable to run it

 

[siddo]

Range("B1").Select

Set prob = ThisWorkbook.Worksheets("ProblemID_afterDupl")
Set rand = ThisWorkbook.Worksheets("Random Transpose")


Set dataRng = prob.Range("A2:B" & LR1)

For y = 1 To Sample

rand.Range("B" & y).Value = Application.WorksheetFunction.VLookup( _
    rand.Range("A" & y).Value, dataRng, 2, False)
   
Next y

Where LR1 has the value of last row from my sheet1 & Sample has the value of last row from sheet2