EXCEL - ADD ADDTIONAL CONDITION INTO VBA CODE

I HAVE A FILE THAT HAS FOUR MACRO BUTTONS - CREATE TAB FOR EACH GROUPNAME - CREATE TAB FOR EACH STAFFNAME - EMAIL - RESET ALL MACRO BUTTONS WORK FINE HOWEVER I NEED ANOTHER CONDITION APPLIED TO THE CREATE TAB FOR EACH GROUPNAME BUTTON THIS BUTTON TAKES INTO ACCOUNT THE START AND END DATE PARAMETER AND ALSO MAX TRADING MONTHS AND MAX TRADING VALUE PARAMETER WHAT IT DOES IS LOOK AT THE RAW DATA HELD IN SHEET 2 (DATA TAB) AND FILTERS ALL NAMES (COLUMN C OF DATA TAB) THAT HAVE TRADED WITHIN THE DATE PARAMETER SELECTED AND CREATE A TAB FOR EACH UNIQUE GROUPNAME HELD IN COLUMN A OF THE DATA TAB. THE NAMES LISTED IN EACH GROUPNAME TAB THEY HAVE SALES FOR THE RESULT WILL SHOW MONTH BY MONTH SALES THE CODE WILL THEN FILTER ALL THOSE NAMES (COLUMN C OF DATA TAB) THAT HAVE TRADED EQUAL TO AND LESS THEN THE VALUE IN THE MAX TRADING MONTH VALUE AND WILL EXCLUDE THOSE NAMES THAT HAVE TRADED MORE THAN THIS VALUE FINALLY THE CODE LOOKS AT THE THE VALUE IN THE MAX TRADING VALUE PARAMETER - ALL NAMES THAT HAVE HAD A GRAND TOTAL HIGHER FOR THE GROUPNAME IN QUESTION IS ALSO EXCLUDED WHAT NEEDS TO BE APPLIED IS WE WANT TO BE ABLE TO PUT A VOLUE OF 0 IN THE MAX TRADING PARAMETER AN 'IF' STATEMENT NNEDS TO BE ADDED SAYING FOR THE CODE TO RUN AS IT IS CURRENTLY EXCEPT WHEN THE VALUE 0 IS KEYED INTO THE MAX TRADING PARAMETER WHEN THE VALUE IS 0 THE CODE NEEDS TO LOOK ALL THE UNIQUE VALUES (NAMES) IN COLUMN C AND FIND ALL THOSE NAMES THAT HAVE HAD SALES IN THE DATE PARAMETER GIVEN AND ALL THIS OTHER NAMES THAT HAVE NOT HAD ANY SALES ARE TO BE DISPLAYED LETS SAY THERE ARE A TOTAL OF 10 UNIQUE NAMES (COLUMN C OF DATA TAB) WHO HAVE ALL HAD SALES OVER A 12 MONTH PERIOD i USE A START AND END DATE PARAMETER OVER TWO MONTHS SAY FROM FEB TO MARCH WITH A MAX TRADING MONTH VALUE OF 0 IF I CLICK ON THE 'CREATE TAB FOR EACH GROUPNAME' MACRO BUTTON THE CODE WILL FIRST FIND THE 10 UNIQUE NAMES IN COLUMN C OF DATA TAB (LETS SAY THE NAMES ARE CALLED CUSTOMER 1 TO CUSTOMER 10) THNE IDENTIFY THOS NAMES THAT HAVE SALES IN THE MONTHS FEB AND MARCH AND CAN SEE THAT CUSTOMER ONE THROUGH TO CUSTOMER 9 HAVE ALL HAD SALES HOWEVER CUSTOMER 10 DID NOT HAVE ANY SALES IN THIS MONTH SO THE RESULT IS CUSTOMER 10