Data validation with formulas

[craigproudfoot]

Hi

This one has me beat.

I have attached an example excel sheet to clarify what I am looking for and I will list the procedures here:
B11 is given a value from a drop down list
C11 is also given a value from a data validation list either "YES" or "X"
I would like to have an automatic process whereby
If B11 value is set to "CASH" - C11 changes to (fill colour green) and "YES"
I have managed to get it to change colour to green with a conditional format, but I can't change the C11 cell value to "YES"
I would like it to work so that if you then change the value of B11 to something other than "CASH", you have the option to set a new value of either "YES" or "X" from the drop down list in C11.

I would also like for C11 to be blank with no fill if B10 =0 - likewise i would like the formulas, drop down lists and formatting to work no matter when the values are changed or how many times they are changed.

I suspect this cannot be done without using VBA (which I have never used), but any pearls would be much appreciated.

This spreadsheet will be for personal use to track receipts and expenditure.

Thank you in advance

Craig