This is one of a number of possible solutions. Right click the sheet tab and select View Code. Copy and paste in
Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
Dim MoveAmount As Variant, MoveTo As Range
Cancel = True
MoveAmount = Application.InputBox("Enter amount to transfer", Type:=1)
If TypeName(MoveAmount) = "Boolean" Then Exit Sub
Set MoveTo = Application.InputBox("Select the destination cell", Type:=8)
MoveTo.Value = MoveTo.Value + MoveAmount
Target.Value = Target.Value - MoveAmount
then close the code window using the X.
Now, to move an amount double click the cell that you want to move the money from. You will be prompted to enter the amount - just enter the number with no £ sign. If you double clicked the cell by accident just click the cancel button.
You will then be prompted for the cell to transfer the money to. You can either type in a cell address like A4 or simply click in the destination cell and click OK.