I have a list of client references, in a 4-digit number format, in column A
of my worksheet. (In Format Cells, Custom was selected and '0000' entered in
as the type, i.e. 430 should appear as 0430.)

I have an additional column which changes each of the references into text,
using the formula below.

=IF(ISNUMBER(A13),FIXED(A13,0,TRUE),"")

However, when changed to text, the format is lost, i.e. '0430' will appear
as '430'. I need any additional zero's to be prefixed where necessary.

Is there any way to do this when the value is set as text?