It depends on how you put your checkmark in.
Put a checkmark in by selecting start:run|Charmap
Select wingdings font and copy the checkmark to the clipboard.
Paste it in Excel and use the pasted checkmark every time you want one.
For it to show as a checkmark your cell must be formatted with Wingding font
then in A1 use the conditional format
=B1=CHAR(252)
Drag down as required and when you paste a checkmark in Col B, Col A turns
whatever colour you chose.
Mike