Help with an "if" formula

[gandyling]

Hello im after some help

I have a spreadsheet and in column A I have a date and then in column B there is another date. I need to have a formula which can calculate the days passed between each date (which is easy enough) but if the cell is blank it would need to calculate the days passed between column A and the current date. Please can someone help I think I need an if formula but im not sure.

[arthurbr]

Maybe =IF(B1="",today()-A1,B1-A1)

[gandyling]

Hi thanks for that it works like a charm!

[gandyling]

Thanks for your help I need a little more help, is there any way the formula could return a blank cell if there are no dates at all?

Thanks again

[Mick2011]

=if(isblank(a1),"",if(b1="",today()-a1,b1-a1))

[gandyling]

Thanks thats perfect