Visual Basic Excel Macro - excel

Question

I want to have a little Macro in excel. The Macro should take a double number from A1 and multiply this number by 5 and return it back into A1 but i always get error messages etc.
My code up to now:
Function multiply()
Dim a As Long
For a = 1 To 65563
cell(a,3) = cell(a,3).Value * 5
next a
End Function
I have not worked with VBA before.

Answer 1

That does what you ask, but it's a sub as you can't edit worksheet values using a function
Public Sub multiply()
On Error GoTo err
Dim val As Long
val = ActiveSheet.Cells(1, 1).Value
ActiveSheet.Cells(1, 1).Value = val * 5
Exit Sub
err:
End Sub

Answer 2

you dont need to use function just use these subs:
bellow you can multiplay all of *column A * values:
Sub example()
For a = 1 To 65563
Cells(a, 1).Value = Cells(a, 1).Value * 5
Next a
End Sub
considering 65563 CELLS isn't a good idea, i suggest you to use the sub bellow to count rows and reduce memory usage.
Sub example2()
Dim countrows As Long
countrows = Range("A" & Rows.Count).End(xlUp).Row
For a = 1 To countrows
Cells(a, 1).Value = Cells(a, 1).Value * 5
Next a
End Sub

Answer 3

You don't actually need a macro for this - although if you do want to use VBA you can avoid time consuming loops altogether
1 Manual Method using Paste Special - Multiply
from walkenbach
To increase a range of values by 5 times:
Enter 5 into any blank cell.
Select the cell and choose Edit, Copy.
Select the range of values (Column A in your example) and choose Edit, Paste Special.
Choose the Multiply option and click OK.
Delete the cell that contains the 5
2 Code using Paste Special - Multiply
Using Zack Barresse's code from vbax - with minor amendments
This code updates the selected range with a user-entered multiplier
Sub psMultiply()
' http://www.vbaexpress.com/kb/getarticle.php?kb_id=47
Dim y As Long 'The multiplier value, user-defined
Dim x As Range 'Just a blank cell for variable
Dim z As Range 'Selection to work with
Set z = Selection
y = Application.InputBox("Enter selection multiplier:", _
Title:="Selection multiplier", Default:=10, Type:=1)
Set x = Cells(Rows.Count, "A").End(xlUp).Offset(1)
If y = 0 Then Exit Sub 'Cancel button will = 0, hence cancel
If x <> "" Then
Exit Sub
Else: x.Value = y
x.Copy
z.PasteSpecial Paste:=xlPasteAll, Operation:=xlMultiply
Application.CutCopyMode = False 'Kill copy mode
End If
x.ClearContents 'Back to normal
End Sub

Answer 4

Why not make it a little more generic by only multiplying the numbers you select:
Sub MultiplyByFive()
Dim cl As Range
For Each cl In Selection
cl = cl * 5
Next cl
End Sub
This way you avoid the 65536 hard coding.