Adjust VBA Code to Run Only When Cells in Certain Range are Changed

Hey everyone - first time poster here.

I've managed to piece together a VBA code that works perfectly for my needs. The problem is that the sheet it is on gets adjusted a lot, and I only need the code to run when certain cells are changed (rather than each time any cell is changed).

Here is the code I have now:

Option Explicit

Private Sub Worksheet_Calculate()
    CheckGoalSeek
End Sub

Private Sub CheckGoalSeek()
    Static isWorking As Boolean

    With Sheet1
        If Not isWorking Then
            isWorking = True
            .Range("EqCost1").Value = 0
            .Range("GMDeal1").GoalSeek Goal:=.Range("GoalGM"), ChangingCell:=.Range("EqCost1")
            .Range("EqCost2").Value = 0
            .Range("GMDeal2").GoalSeek Goal:=.Range("GoalGM"), ChangingCell:=.Range("EqCost2")
            .Range("EqCost3").Value = 0
            .Range("GMDeal3").GoalSeek Goal:=.Range("GoalGM"), ChangingCell:=.Range("EqCost3")
            .Range("EqCost4").Value = 0
            .Range("GMDeal4").GoalSeek Goal:=.Range("GoalGM"), ChangingCell:=.Range("EqCost4")
            .Range("EqCost5").Value = 0
            .Range("GMDeal5").GoalSeek Goal:=.Range("GoalGM"), ChangingCell:=.Range("EqCost5")
            isWorking = False
        End If
    End With
End Sub

Put simply, I need this code to run only when a cell in Range "TValueDeal" is changed. Is making this adjustment as simple as adding a couple lines of code, or is there a better way to write the entire thing?

Thanks for your help.