Creating a vba loop that grabs cell values - excel

Question

I'm trying to create a macro for vba that grabs values entered in my A column of cells 1-1000, and then takes those values and plugs them into an function.
Rather than define a 1000 different values as:
x1 = Worksheets("Sheet1").Range("A1").Value
x2 = Worksheets("Sheet1").Range("A2").Value
x3 = Worksheets("Sheet1").Range("A3").Value
... etc
and then plugging them into my function
Dim dy As Integer, fx As Integer
dy = Range("B2").Value - Range("B1").Value
fx= dy*(x1+x2+x3....)
is there someway I can create a do loop that runs from cell A1 to A1000 grabbing each of their own values and plugging it into my function? Here's what I have so far but I'm not sure how I would have it grab the values entered in the cells.
xi = 1
Do
xi = 1 + xi
If xi = 1000 Then Exit Do
Count = Count + 1
Loop

Answer 1

'create a zero-based array o9f the values in A1:A1000
dim x as variant
with Worksheets("Sheet1")
x = application.transpose(.range("A1:A1000").value)
end with
'sum all of x
dim i as long, sumX as double
for i = lbound(x) to ubound(x)
sumX = sumX + x(i)
next i
'another way to sum A1:A1000
with Worksheets("Sheet1")
sumX = application.sum(.range("A1:A1000").value)
end with
'your function
Dim dy As long, fx As long
with Worksheets("Sheet1")
dy = .Range("B2").Value - .Range("B1").Value
end with
fx = dy * sumX

Answer 2

Below Query Works for you. The code flexible to get the row count in column "A". No need to hard code the upper bound value
Dim dy As Integer, fx As Integer, iCellSum As Integer
Sub Main()
iRowCount = Sheets("Sheet1").Range("A" & Rows.Count).End(xlUp).Row
iCellSum = 0
For i = 1 To iRowCount
iCellSum = iCellSum + Sheets("Sheet1").Cells(i, 1)
Next
dy = Range("B2").Value - Range("B1").Value
fx = dy * iCellSum
End Sub