Conditional format? Need indicator based on adjacent cell

I am looking to have a cell conditionally display a character (such as a dash [that is the character between the following quotes "-"]) based on the value of an adjacent cell such that if there is a value present the dash will not appear but if there is a value present the dash will appear. In this way I can be alerted to lines in my spreadsheet for which there is no value present. The setup in mind I have is as follows:

Column A: set this to conditionally display the "-" based on the contents of column c
Column B: product name
Column C: product value

In this way i intend for column a to be completely empty when all of the products have corresponding values, and for column A to indicate (and draw attention) to when i have failed to input a value for a product.

An example of what I have in mind follows:

I would fill in the following cells, rows 1-3 in columns A and B
*note that the brackets [] indicate the contents of the hereinbefore noted cell organized in as close to the spreadsheet format as I can type out in this forum

B1[Product Alpha] C1[5] --> there is a value present in C1 that corresponds to the product in B1 so A1 should be blank
B2[Product Beta] C2[] --> there is no value present in C2 that corresponds to the product in B2 so A2 should automatically show a "-"
B3[Product Gamma] C3[7] --> there is a value present in C3 that corresponds to the product in B3 so A3 should be blank

Therefore in this setup after my spreadsheet is set to automatically fill A based on the presence or absence of a value in C the spreadsheet after typing in the contents of columns B and C as noted above would look like this:

A1[] B1[Product Alpha] C1[5]
A2[-] B2[Product Beta] C2[]
A3[] C3[Product Gamma] C3[7]

Thank you for your help, I really appreciate it.