Storing row numbers

[jolivanes]

This should be a start on getting the row numbers as requested.
For this to work, there need to be a space between "Parameter" and the number following it, like you have except with "Parameter5".

Sub Get_Row_Numbers()
Dim a As Long, TopRow As Long, LastRow As Long
a = InputBox("Which Parameter do want to graph?", "Enter Parameter number")
    TopRow = Columns(1).Find("Parameter " & a).Row + 1
    LastRow = Cells(TopRow, 3).End(xlDown).Row
    
MsgBox TopRow
MsgBox LastRow
End Sub